Methods of treating middle-of-the-night insomnia

ABSTRACT

The present invention provides compositions and methods for treating middle-of-the-night insomnia without residual sedative effects upon awakening by administering low doses (about 5 mg or less) of zolpidem or a salt thereof.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.60/684,842, filed May 25, 2005, U.S. Provisional Application No.60/741,673, filed Dec. 1, 2005, U.S. Provisional Application No.60/788,340, filed Mar. 31, 2006, and U.S. Provisional Application No.60/788,249, filed Mar. 31, 2006, the disclosures of which are herebyincorporated by reference in their entirety for all purposes.

BACKGROUND OF THE INVENTION

Until recently, medical literature has recognized four types ofinsomnia, including sleep onset insomnia (e.g., trouble falling asleepat bedtime), sleep maintenance insomnia (e.g., disturbed sleep duringthe night), early morning awakening, and transient insomnia (e.g., newenvironment, first night in hotel syndrome). However, according to theNational Sleep Foundation's 2005 “Sleep in America” poll, about 20% oftotal respondents and about 50% of respondents reporting insomniasymptoms complained of waking up too early and having difficultyreturning to sleep at least a few nights a week (results available onthe worldwide web at sleepfoundation.org). This type of insomniaincludes “middle-of-the-night” insomnia, “late night” insomnia,“prolonged awakening after sleep onset” insomnia, “sleep maintenance”insomnia, and insomnia that follows after “middle-of-the-night”awakening, each of which has a component of interrupted sleep.

More particularly, patients with “middle-of-the-night” (MOTN) insomniagenerally do not have problems initially falling asleep, but wake upprior to their intended wake time (during their normal sleep time),usually with about 3 to 4 hours of sleep time remaining. These patientsrequire a treatment intervention that would reduce their wake timeduring their sleep time after awakening without leaving residualsedative effects in the morning. Unfortunately, currently availablehypnotic medications are unsuitable for treating MOTN insomnia becausethey are slow to induce sleep (e.g., zaleplon) and/or requireadministration prior to about 7 to 9 hours in bed to avoid residualsleepiness in the morning (e.g., available dosage forms of zolpidem,eszopiclone, and zopiclone). Also, administration of most presentlyavailable hypnotics is prophylactic, resulting in unnecessary medicationand overmedication of persons who require treatment for their MOTNinsomnia a few nights a week.

Clearly, there remains a need for appropriate treatments for personswith MOTN insomnia. The present invention fulfills this and other needs.

BRIEF SUMMARY OF THE INVENTION

The present invention provides compositions and methods for treatingMOTN insomnia with zolpidem or a salt thereof.

In one aspect, the present invention provides a solid unit dosagecomposition for the treatment of MOTN insomnia, the compositioncomprising an effective amount of zolpidem or a salt thereof, formulatedfor delivery of zolpidem across a subject's oral mucosa, wherein theeffective amount is an amount of less than 1.30×10⁻⁵ moles of zolpidem,and is an amount sufficient to produce a plasma concentration betweenabout 25 ng/ml and about 50 ng/ml within 20 minutes of administration,when evaluated in an appropriate patient population.

In another aspect, the present invention provides a solid unit dosagecomposition for the treatment of MOTN insomnia, the compositioncomprising an amount of zolpidem or a salt thereof effective to producesleep within 30 minutes of dosing a subject, but does not produceresidual sedative effects when the subject is awakened at a time about 4hours after dosing, when the composition is evaluated in an appropriatepatient population.

In yet another aspect, the present invention provides a pharmaceuticalcomposition suitable for absorption by the oral mucosa in the treatmentof MOTN insomnia, the composition comprising from about 0.5 mg to about4.0 mg of zolpidem or a salt thereof and a pharmaceutically acceptableexcipient.

In a further aspect, the present invention provides a solidpharmaceutical composition for delivery across the oral mucosa fortreating insomnia comprising zolpidem in an amount less than 5 mg and abuffer.

In a related aspect, the present invention provides a solidpharmaceutical composition for delivery across the oral mucosa fortreating insomnia comprising zolpidem in an amount less than 5 mg and abinary buffer.

In another related aspect, the present invention provides a solid unitdosage pharmaceutical composition comprising a dose of zolpidemhemitartrate in an amount of less than 5 mg and a binary buffer systemcapable of raising the pH of a subject's saliva to a pH greater thanabout 8.5, irrespective of the starting pH of saliva, wherein thecomposition is formulated for delivery of zolpidem across the subject'soral mucosa.

In an additional aspect, the present invention provides a pharmaceuticalcomposition for treating insomnia comprising zolpidem in an amount lessthan 5 mg and a binary buffer.

In a related aspect, the present invention provides a pharmaceuticalcomposition for treating insomnia comprising zolpidem in an amount lessthan 5 mg and a binary buffer, wherein the composition is formulated fordelivery of zolpidem across the oral mucosa and the binary bufferproduces a saliva pH of at least 8.5, irrespective of the startingsaliva pH.

In another aspect, the present invention provides a method of treatinginsomnia, the method comprising:

-   -   administering to a subject who awakens from sleep and desires to        return to sleep within 30 minutes and sleep for less than 5        hours, a single unit dosage composition comprising an effective        amount of zolpidem or a salt thereof, formulated for delivery of        zolpidem across the subject's oral mucosa,    -   wherein the effective amount is an amount of less than 1.30×10⁻⁵        moles of zolpidem, and is an amount sufficient to produce a        plasma concentration between about 25 ng/ml and about 50 ng/ml        within 20 minutes of administration, when evaluated in an        appropriate patient population.

In a related aspect, the present invention provides a method of treatingMOTN insomnia in a subject, the method comprising:

-   -   administering to the subject a pharmaceutical composition        comprising zolpidem or a salt thereof in an amount of less than        1.30×10⁻⁵ moles of zolpidem,

wherein the administering is on an as-needed basis, and wherein deliveryof zolpidem occurs across the subject's oral mucosa to produce a bloodlevel of zolpidem in the subject between about 25 ng/ml and about 50ng/ml within about 20 minutes of administration and less than 20 ng/mlat a time 4 hours after administration.

In yet another aspect, the present invention provides a method oftreating insomnia in a subject, the method comprising:

-   -   administering to the subject a pharmaceutical composition        comprising zolpidem or a salt thereof,

wherein the composition provides delivery of zolpidem across thesubject's oral mucosa, wherein the subject is a subject who awakens fromsleep and desires to resume sleep for less than 5 hours, and wherein thecomposition produces sleep within 30 minutes of dosing and the dose issuch that it does not produce residual sedative effects when the subjectis awakened at a time 4 hours after dosing.

In a further aspect, the present invention provides a method of treatinginsomnia in a subject, the method comprising:

-   -   administering a solid pharmaceutical composition comprising        zolpidem in an amount less than 5 mg and a buffer, to a subject        who awakens from sleep and desires to resume sleep for less than        5 hours,

wherein the solid pharmaceutical composition provides delivery ofzolpidem across the subject's oral mucosa, and wherein a blood level ofzolpidem is achieved in the subject of between about 25 ng/ml and about50 ng/ml within about 20 minutes of administration.

In a related aspect, the present invention provides a method of treatinginsomnia, the method comprising the steps of:

-   -   providing a solid pharmaceutical composition comprising zolpidem        in an amount less than 5 mg and a buffer to a patient who        awakens from sleep and desires to resume sleep for less than 5        hours; and    -   administering the solid pharmaceutical composition to the        patient for delivery of the zolpidem across the patient's oral        mucosa,

wherein a blood level of zolpidem in the patient is between about 25ng/ml and about 50 ng/ml within about 20 minutes of administration.

In an additional aspect, the present invention provides a method oftreating insomnia, the method comprising:

-   -   administering a solid pharmaceutical composition comprising        zolpidem in an amount less than 5 mg and a binary buffer, to a        subject who awakens from sleep and desires to resume sleep for        less than 5 hours,

wherein the solid pharmaceutical composition provides delivery ofzolpidem across the subject's oral mucosa, wherein the solidpharmaceutical composition dissolves or disintegrates in about 2 minutesor less in the subject's mouth, and wherein the binary buffer raises thepH of saliva in the subject's mouth to a pH greater than about 9.0.

In a related aspect, the present invention provides a method of treatinginsomnia, the method comprising the steps of:

-   -   providing a solid pharmaceutical composition comprising zolpidem        in an amount less than 5 mg and a binary buffer to a patient who        awakens from sleep and desires to resume sleep for less than 5        hours; and    -   administering the solid pharmaceutical composition to the        patient for delivery of the zolpidem across the patient's oral        mucosa,

wherein the solid pharmaceutical composition dissolves or disintegratesin about 2 minutes or less in the patient's mouth, and wherein thebinary buffer raises the pH of saliva in the patient's mouth to a pHgreater than about 9.0.

Other objects, features, and advantages of the present invention will beapparent to one of skill in the art from the following detaileddescription and figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the mean (SEM) plasma concentration time profiles of a 1.0mg, 1.75 mg, and 3.5 mg sublingual zolpidem lozenge of the presentinvention.

FIG. 2 shows the predicted versus observed plasma profiles of a 1.0 mg,1.75 mg, and 3.5 mg sublingual zolpidem lozenge of the presentinvention.

FIG. 3 shows the Digit Symbol Substitution Test (DSST) scores of a 1.0mg, 1.75 mg, and 3.5 mg sublingual zolpidem lozenge of the presentinvention as a function of time.

FIG. 4 shows the DSST scores of a 1.0 mg, 1.75 mg, and 3.5 mg sublingualzolpidem lozenge of the present invention as a function of plasmaconcentration.

FIG. 5 shows a comparison of DSST scores of a 3.5 mg sublingual zolpidemlozenge of the present invention and 5 mg and 10 mg peroral (PO) Ambien®as reported in the literature.

FIG. 6 shows the Visual Analog Scale (VAS) scores of a 1.0 mg, 1.75 mg,and 3.5 mg sublingual zolpidem lozenge of the present invention.

FIG. 7 shows the change in reaction time scores as measured by aPsychomotor Vigilance Test (PVT) of a 1.0 mg, 1.75 mg, and 3.5 mgsublingual zolpidem lozenge of the present invention.

DETAILED DESCRIPTION OF THE INVENTION I. General

The present invention provides compositions and methods for treatinginsomnia, particularly MOTN insomnia, using therapeutically effectivelow doses of zolpidem or a salt thereof by delivering zolpidem acrossthe oral mucosa. The present invention is based, in part, upon thesurprising discovery that low doses of zolpidem, when formulated fordelivery across the oral mucosa, can induce rapid onset of sleep withoutresidual sedative effects upon awakening 2-4 hours later. Advantages oftaking a low dose amount of zolpidem (e.g., less than 5 mg or 1.30×10⁻⁵moles) to counteract MOTN insomnia include rapid action to induce sleep,treatment on an as-needed basis to avoid excessive and unnecessarymedication, and no or minimal residual sedative effects upon awakening.

While there are various types of dosage forms, solid dosage forms fororal administration are perhaps among the most preferred by patients,and among the most prevalently used. Many of the dosage forms aremedicaments formulated as tablets or capsules, which are swallowed.However, swallowed formulations have several disadvantages, includingdrug losses during hepatic first pass metabolism, during enzymaticdegradation within the gastrointestinal tract, and during absorption tonon-targeted tissues. These drug losses not only increase thevariability in drug response, but also often require that the medicamentbe given in greater initial doses. Still further, as the drug has topass through the gastrointestinal system in order to enter the bloodstream, the time to reach a therapeutic effect may be quite long,typically around forty-five minutes or longer.

Drug delivery via the mucous membranes of the oral cavity has certainadvantages, due to the properties of the oral mucosa itself. Forexample, the mucous membranes of the oral cavity are highly vascularizedand well supplied with lymphatic drainage sites. In general, the mucousmembranes of the oral cavity can be divided into five main regions: thefloor of the mouth (sublingual), the cheeks (buccal), the gums(gingival), the roof of the mouth (palatal), and the lining of the lips.These regions differ from each other with respect to their anatomy, drugpermeability, and physiological response to drugs. For example, in termsof permeability, sublingual is more permeable than buccal, which is morepermeable than palatal. This permeability is generally based on therelative thickness and degree of keratinization of these membranes, withthe sublingual mucosa being relatively thin and non-keratinized, thebuccal mucosa being thicker and non-keratinized, and the palatal mucosabeing intermediate in thickness, but keratinized.

Accordingly, in certain aspects, the present invention provides soliddosage forms containing low doses of zolpidem (e.g., dissolving tablets,lozenges, etc.) and methods for treating MOTN insomnia by administeringsuch compositions to the oral mucosa to deliver and facilitateabsorption of a substantial portion of the dose through the tissues ofthe buccal and/or sublingual cavity. In some embodiments, the soliddosage forms described herein facilitate buccal and/or sublingualabsorption due to the presence of a buffer system (e.g., abicarbonate/carbonate buffer system). Without being bound to anyparticular theory, the buffer system can promote the in situ conversionof a hydrophilic (i.e., charged) form of zolpidem (e.g., zolpidemhemitartrate) into its lipophilic free-base (i.e., neutral) form, whichpenetrates the lipid membranes in the oral mucosa more readily than thesalt form. As a result, both non-elderly and elderly patients canbenefit from taking a substantially lower dose of zolpidem (e.g., about3.5 mg for non-elderly; about 1.75 mg for elderly) as compared to thelowest currently approved dose of 5 mg, thereby rapidly inducing sleepwithout residual sedative effects upon awakening.

It is also desirable to reduce variability in drug delivery.Surprisingly, this can be achieved by utilizing a binary buffer systemcapable of achieving and sustaining a final pH in the oral cavity,independent of the initial pH. Accordingly, compositions for deliveringzolpidem or a salt thereof across the oral mucosa having a buffer systemthat produces a final pH, independent of the initial pH, and whichsustains that final pH for a given period of time, are particularlydesirable, and are provided herein.

II. Definitions

As used herein, the following terms have the meanings ascribed to themunless specified otherwise.

The term “sleep disorder” refers to a disruptive pattern of sleeparising from many causes including, without limitation, dysfunctionalsleep mechanisms, abnormalities in physiological functions during sleep,abnormalities of the biological clock, and sleep disturbances that areinduced by factors extrinsic to the sleep process. In particular, theterm encompasses disorders associated with difficulties in stayingasleep and/or falling asleep such as insomnia (e.g., transient,short-term, and chronic), delayed sleep phase syndrome,hypnotic-dependent sleep disorder, and stimulant-dependent sleepdisorder; disorders associated with difficulties in staying awake suchas sleep apnea, narcolepsy, restless leg syndrome, obstructive sleepapnea, central sleep apnea, idiopathic hypersomnia, respiratory muscleweakness-associated sleep disorder; disorders associated withdifficulties in adhering to a regular sleep schedule such as sleep statemisperception, shift work sleep disorder, chronic time zone changesyndrome, and irregular sleep-wake syndrome; disorders associated withabnormal behaviors such as sleep terror disorder (i.e., parasomnia) andsleepwalking (i.e., somnambulism); and other disorders such as sleepbruxism, fibromyalgia, and nightmares.

The term “insomnia” refers to a sleep disorder characterized by symptomsincluding, without limitation, difficulty in falling asleep, difficultyin staying asleep, intermittent wakefulness, and/or waking up too early.The term also encompasses daytime symptoms such as sleepiness, anxiety,impaired concentration, impaired memory, and irritability. Types ofinsomnia suitable for treatment with the compositions of the presentinvention include, without limitation, transient, short-term, andchronic insomnia. The term “transient insomnia” refers to insomnialasting for a few nights. The term “short-term insomnia” refers toinsomnia lasting for about two to about four weeks. The term “chronicinsomnia” refers to insomnia lasting for at least one month.

The phrase “prolonged awakening after sleep onset insomnia” refers tothe condition wherein a subject, after falling asleep, awakens and hasdifficulty returning to sleep, regardless of the number of hours of timein bed remaining. “Prolonged awakening after sleep onset insomnia”includes middle-of-the-night insomnia, late night insomnia, and insomniaafter early night awakening.

As used herein, the term “middle-of-the-night insomnia” or “MOTNinsomnia” refers to the condition wherein a subject, after fallingasleep, awakens and has difficulty returning to sleep. Typically, thesubject has about 5 hours of sleep time or time in bed remaining,although in some subjects only 4 hours, 3 hours, or 2 hours of sleeptime may remain. One of skill in the art will appreciate that the termmiddle-of-the-night refers to a middle portion of the subject's sleeptime in any sleep period, rather than a specific time of a time zone,day or night. For example, a shift worker who would normally sleep from8 am until 3 pm or 4 pm can still exhibit MOTN insomnia, when theirsleep time is interrupted during normal daylight hours. MOTN insomniacan be transient, short-term, or chronic.

The term “time in bed” refers to the amount of time a subject spends ina recumbent position (e.g., lying down in bed or reclining in a chair)intending to sleep.

The term “sleep time” refers to the time that a subject spends sleeping.Sleep time can be continuous or discontinuous.

“Sleep efficiency” refers to the total sleep time a subject receivesduring their time in bed. Sleep efficiency is measured by the followingequation:100*(total sleep time (TST)/total time in bed).

The phrase “residual sedative effects” refers to a patient's subjectivefeeling of sedation upon awakening. Additionally, the term is meant torefer to a patient population as found in, for example, a clinicaltrial, rather than a single patient example. Residual sedative effectsalso can be evaluated using one or more of any of a number of testsexploring psychomotor performance, attention, information processing,and memory used by those of skill in the art including, for example, aSleep Latency Test (SLT), a Visual Analog Test (VAT), a Digit SymbolSubstitution Test (DSST), a Symbol Copying Test (SCT), a CriticalFlicker Fusion threshold test (CFF), a Simple Reaction time test (visualor auditory; SRT), a Choice Reaction Time test (CRT), a Word LearningTest (WLT), a Critical Tracking Test (CTT), a Divided Attention Test(DAT), a digit or letter cancellation test, sleep staging throughpolysomnographic (PSG) measurements, Continuous Performance Task test(CPT), Multiple Sleep Latency Test (MSLT), a Rapid Visual InformationProcessing test (RVIP), a mental calculation test, a body sway test, adriving performance test, and others. Guidelines for a Sleep LatencyTest are published in Sleep (1986) 9:519-24. The above-listed tests aredescribed, for example, in Walsh, et al., (2000) Clin Neuropharm23:17-21; Verster, et al., (2002) J Clin Psychopharm 22:576-583; Patat,et al, (2001) Human Psychopharm 16:369-392; and Hindmarch, et al.,(2001) Human Pshychopharm 16:159-167. As a result, an amount thatsubstantially avoids or does not produce residual sedative effects is anamount that allows a subject, upon awakening following sleep time, totest acceptably in at least one of the above tests, preferably at leasttwo or three of the above tests, and most preferably in at least four ofthe above tests.

Alternatively, an amount that substantially avoids or does not produceresidual sedative effects can be objectively measured by determining theplasma or serum levels of zolpidem at an appropriate time point. Inparticular, residual sedative effects will be essentially extinguishedwhen a subject's plasma levels of zolpidem fall below about 20 ng/ml.Again, this objective test refers to an average zolpidem plasma or serumconcentration in a patient population. Because some variability betweenpatients is expected, a number of patients may respond as havingresidual sedative effects even at low plasma or serum concentrations ofzolpidem.

The term “therapeutically effective amount” or “effective amount” refersto the amount of zolpidem that is capable of achieving a therapeuticeffect in a subject in need thereof. For example, an effective amount ofzolpidem can be the amount that is capable of preventing or relievingone or more symptoms associated with MOTN insomnia. It is important tonote that a plasma concentration time curve for any given drug isillustrative of four, very often overlapping, kinetic events that decidethe fate of the drug inside the body after the drug is administered. Thefour events are absorption, distribution, metabolism, and excretion. Theabsorption phase dominates in the beginning, while the distributionphase dominates at peak concentration time, and metabolism and excretionphases dominate the remaining disappearing stages of the drug. Thesedative-hypnotic activity profile of zolpidem can be predicted from itsplasma concentration time curve (Greenblatt et al., Clin. Pharmacol.Therap. 64:553 (1998)). In general, plasma concentrations between about25 ng/ml and about 50 ng/ml, which are sufficient for inducing sleep,occur during the absorption phase of the drug, but this is notnecessarily the peak concentration. Once the zolpidem is absorbed anddistributed, the plasma concentrations will fall off with time. When thelatter phase of drug distribution, metabolism, and excretion results inconcentrations of zolpidem below about 20 ng/ml, the residual sedativeeffects of the drug will be essentially extinguished. This level willdepend, to some extent, on the patient's age, hepatic efficiency, andinitial dose. Generally, for the compositions and methods describedherein, the sedative-hypnotic activity does not persist once the plasmalevels have dropped below about 20 ng/ml, due to concurrence ofcontinuous depletion of drug in the body and fulfillment of sleeprequirement of the sleep-wake cycle of the body.

The term “bioavailability” refers to the rate and/or extent to which adrug is absorbed or becomes available to the treatment site in the body.The MOTN efficacy of zolpidem can also be improved by improving thebioavailability or the absorption of zolpidem, e.g., at rate of about0.1 ng/ml per minute.

The term “dissolves” or “dissolution” refers to the conversion of aportion of the solid dosage form to a solution or slurry form. Theamount of the solid dosage form that dissolves over a period of timewill vary depending on the components of the dosage form (e.g., the formof zolpidem used as well as the excipients used). Some solid dosageforms will completely dissolve in a patient's mouth over a time periodof about 15 minutes or less. Still other solid dosage forms willcompletely dissolve in the mouth over a time period of about 6 minutesor less. Generally, at least about 25% by weight of the solid dosageform will dissolve within about 5 minutes of administration. Suitablemethods known in the art for determining the dissolution profile of asolid dosage form include, e.g., United States Pharmacopeia (USP)dissolution tests such as USP <711> Apparatus 1 or USP <711> Apparatus2.

The term “disintegrates” or “disintegration” refers to the breakdown of,for example, a tablet or lozenge, into small pieces accompanied bycomplete dissolution of a substantial portion of the solid dosage formto a liquid form. More particularly, disintegration of a solid dosageform refers to less than about 25% by weight of the solid dosage formremaining in the mouth following an appropriate time period, e.g., about5 minutes after administration. Suitable methods known in the art fordetermining the disintegration profile of a solid dosage form include,e.g., the USP disintegration test.

As used herein, the phrase “substantially complete conversion ofzolpidem from its ionized to its un-ionized form” refers to greater thanabout 50% conversion of zolpidem from its ionized form into itsun-ionized form. For example, a buffer system may favor at least about50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 99% conversion ofzolpidem from its ionized form into its un-ionized form. In someembodiments, the conversion occurs within about 10 minutes followingadministration.

The term “variability” refers to inter-subject variability in terms ofthe percent of relative standard deviation (RSD) for the maximum plasmaconcentration (C_(max)) and the time to reach the maximum plasmaconcentration (T_(max)). Notably, the preferred compositions of thepresent invention have an RSD for C_(max) of about 33% versus about 45%for commercial oral tablets such as Ambien® tablets. Further, thecompositions of the present invention have an RSD for T_(max) of about50% or less versus about 100% for commercial oral tablets such asAmbien® tablets.

The term “subject” or “patient” refers to humans.

The term “administering” refers to administration of the compositions ofthe present invention to the mucous membranes of the oral cavity (i.e.,oral mucosa). Examples of suitable sites of administration within theoral mucosa include, without limitation, the mucous membranes of thefloor of the mouth (sublingual mucosa), the cheeks (buccal mucosa), thegums (gingival mucosa), the roof of the mouth (palatal mucosa), thelining of the lips, and combinations thereof. Preferably, thecompositions of the present invention are administered to the sublingualmucosa, buccal mucosa, or a combination thereof.

III. Description of the Embodiments

In one aspect, the present invention provides a solid unit dosagecomposition for the treatment of MOTN insomnia, the compositioncomprising an effective amount of zolpidem or a salt thereof, formulatedfor delivery of zolpidem across a subject's oral mucosa, wherein theeffective amount is an amount of less than 1.30×10⁻⁵ moles of zolpidem,and is an amount sufficient to produce a plasma concentration betweenabout 25 ng/ml and about 50 ng/ml within 20 minutes of administration,when evaluated in an appropriate patient population.

In one embodiment, the solid unit dosage composition provides about 50%of the maximum plasma concentration (C_(max)) of zolpidem in about 30minutes or less, alternatively in about 20 minutes or less, oralternatively in about 10 minutes or less. In another embodiment, thesolid unit dosage composition provides blood (e.g., plasma) levels ofzolpidem that are less than about 20 ng/ml at a time about 2, 3, or 4hours after dosing. The zolpidem is typically delivered across thesubject's sublingual and/or buccal mucosa.

In some embodiments, the solid unit dosage composition comprises atleast one pH-adjusting agent selected from the group consisting of acarbonate salt and a bicarbonate salt. In other embodiments, the solidunit dosage composition comprises a binary buffer system that raises thepH of the subject's saliva to a pH greater than about 8.5, alternativelygreater than about 9.0, alternatively greater than about 9.5,alternatively greater than about 10.0, alternatively greater than about10.5, alternatively greater than about 11.0, or alternatively betweenabout 9.0 and about 11.0, irrespective of the starting pH of saliva. Forexample, the binary buffer system can comprise sodium carbonate andsodium bicarbonate. Alternatively, the binary buffer system can compriseany combination of carbonate salt and bicarbonate salt known in the art.

The solid unit dosage composition is typically in the form of a lozenge,a chewing gum, a chewable tablet, or a dissolving tablet such as aslow-dissolving tablet or a quick-dissolving tablet. Preferably, thesolid unit dosage composition is a lozenge or a quick-dissolving tablet.A quick-dissolving tablet usually provides complete dissolution in thesubject's mouth in less than about 0.5 minutes, alternatively in lessthan about 1 minute, alternatively in less than about 1.5 minutes,alternatively in less than about 2 minutes, alternatively in less thanabout 2.5 minutes, alternatively in less than about 3 minutes,alternatively in less than about 4 minutes, alternatively in less thanabout 5 minutes, or alternatively in less than about 6 minutes. Adescription of low dose zolpidem lozenge and tablet dosage forms isprovided in Examples 1 and 3, respectively.

In another embodiment, the solid unit dosage composition contains lessthan about 5 mg of zolpidem hemitartrate. Preferably, the solid unitdosage composition contains from about 0.5 to about 4.75 mg of zolpidemhemitartrate, alternatively from about 1.5 to about 2.5 mg of zolpidemhemitartrate, or alternatively from about 3.0 to about 3.75 mg ofzolpidem hemitartrate.

The effective amount of zolpidem is generally evaluated in anappropriate patient population (e.g., a patient population used for aclinical study) based on factors such as age, weight, the number ofhours of time in bed remaining, and/or the ability of a subject tometabolize zolpidem. Accordingly, effective amounts of zolpidem fordelivery across the oral mucosa may be different for selected patientpopulations. For example, the effective amount of zolpidem in an elderlypatient population (i.e., subjects 65 years of age and older) is usuallyfrom about 1.5 mg to about 2.5 mg of zolpidem, alternatively about 1.75mg, alternatively about 2.0 mg, or alternatively about 2.5 mg.Similarly, the effective amount of zolpidem in a population of subjectswith a diminished capacity to metabolize zolpidem can be from about 1.5mg to about 2.5 mg of zolpidem, alternatively about 1.75 mg,alternatively about 2.0 mg, or alternatively about 2.5 mg. The effectiveamount of zolpidem in a non-elderly patient population (i.e., subjectsyounger than 65 years of age) is usually from about 3.0 mg to about 3.75mg zolpidem, alternatively about 3.25 mg, alternatively about 3.5 mg, oralternatively about 3.75 mg. The effective amount of zolpidem insubjects who have awakened but still have about 4 or 5 hours of time inbed remaining can be from about 2 mg to about 5 mg of zolpidem. A loweramount of zolpidem (e.g., from about 0.5 mg to about 2.5 mg,alternatively about 0.5 mg, alternatively about 1.0 mg, alternativelyabout 1.5 mg, alternatively about 2.0 mg, or alternatively about 2.5 mg)can be administered to subjects who have awakened but still have about 2to 4 hours of time in bed remaining.

Any method known in the art can be used to determine the plasmaconcentration of zolpidem in a subject. As a non-limiting example, theplasma from a blood sample collected from the subject can be assayed forzolpidem levels using high pressure liquid chromatography (HPLC)followed by tandem mass spectrometry (MS) or fluorescence detection.Chromatographic methods for measuring plasma levels of zolpidem aredescribed in, for example, Ascalone et al., J. Chromatogr., 581:237-250(1992); Tracqui et al., J. Chromatogr., 616:95-103 (1993); Durol et al.,J. Anal. Toxicol., 215:388-392 (1997); Ptacek et al., J. Chromatogr. BBiomed. Sci. Appl., 694:409-413 (1997); and Ring et al., J. Pharm.Biomed. Anal., 22:495-504 (2000).

In another aspect, the present invention provides a solid unit dosagecomposition for the treatment of MOTN insomnia, the compositioncomprising an amount of zolpidem or a salt thereof effective to producesleep within 30 minutes of dosing a subject, but does not produceresidual sedative effects when the subject is awakened at a time about 4hours after dosing, when the composition is evaluated in an appropriatepatient population.

In some embodiments, the solid unit dosage composition further comprisesat least one pH-adjusting agent. Examples of pH-adjusting agentsinclude, but are not limited to, carbonate salts, bicarbonate salts, andmixtures thereof. In other embodiments, the solid unit dosagecomposition comprises a binary buffer system. As a non-limiting example,the binary buffer system can comprise a carbonate salt (e.g., sodiumcarbonate) and a bicarbonate salt (e.g., sodium bicarbonate). In apreferred embodiment, the solid unit dosage composition is in a dosageform suitable for delivery of zolpidem across the subject's oral mucosa(e.g., buccal and/or sublingual delivery), wherein the binary buffersystem raises the pH of the subject's saliva to a pH greater than about8.5, alternatively greater than about 9.0, alternatively greater thanabout 9.5, alternatively greater than about 10.0, alternatively greaterthan about 10.5, alternatively greater than about 11.0, or alternativelybetween about 9.0 and about 11.0, irrespective of the starting pH ofsaliva.

In certain embodiments, the solid unit dosage composition producespolysomnography stage 1 sleep at the onset of sleep. Polysomnographystage 1 sleep typically refers to a non-REM stage of sleep where apolysomnogram shows about a 50% reduction in activity from wakefulness.The eyes are usually closed during polysomnography stage 1 sleep, but ifaroused from it, a subject may feel as if he or she has not slept.Polysomnography stage 1 sleep may last for about 5 to about 10 minutes.

In another embodiment, the solid unit dosage composition contains lessthan about 5 mg of zolpidem hemitartrate. Preferably, the solid unitdosage composition contains from about 0.5 to about 4.75 mg of zolpidemhemitartrate, alternatively from about 1.5 to about 2.5 mg of zolpidemhemitartrate, or alternatively from about 3.0 to about 3.75 mg ofzolpidem hemitartrate.

The solid unit dosage composition is typically in the form of a lozenge,a tablet (e.g., chewable tablet, slow-dissolving tablet,quick-dissolving tablet), or a chewing gum. Preferably, the compositionis a lozenge or a quick-dissolving tablet. In some embodiments, thesolid unit dosage composition provides buccal and/or sublingualdissolution in about 5 minutes or less (e.g., about 4, 3, 2, 1, or 0.5minutes or less) following administration.

In yet another aspect, the present invention provides a pharmaceuticalcomposition suitable for absorption by the oral mucosa (e.g., buccaland/or sublingual absorption) in the treatment of MOTN insomnia, thecomposition comprising from about 0.5 mg to about 4.0 mg of zolpidem ora salt thereof and a pharmaceutically acceptable excipient.

In some embodiments, the pharmaceutical composition comprises from about0.5 to about 4.0 mg of zolpidem hemitartrate. Generally, thepharmaceutical composition can comprise about 1.0 mg, alternativelyabout 1.75 mg, alternatively about 2.5 mg, alternatively about 3.0 mg,or alternatively about 3.5 mg, of zolpidem or a salt thereof such aszolpidem hemitartrate. In other embodiments, the pharmaceuticalcomposition further comprises a binary buffer system. For example, thebinary buffer system can comprise a carbonate such as sodium carbonateand a bicarbonate such as sodium bicarbonate. The carbonate andbicarbonate are usually present in a carbonate:bicarbonate ratio of fromabout 1:1.0 to about 1:1.4 by weight, or alternatively from about 1:1.0to about 1:1.2 by weight. Preferably, the binary buffer system raisesthe pH of the subject's saliva to a pH greater than about 8.5,alternatively greater than about 9.0, alternatively greater than about9.5, alternatively greater than about 10.0, alternatively greater thanabout 10.5, alternatively greater than about 11.0, or alternativelybetween about 9.0 and about 11.0, irrespective of the starting pH ofsaliva.

In certain embodiments, the pharmaceutical composition is a solid unitdosage form such as a lozenge or tablet (e.g., chewable tablet,slow-dissolving tablet, quick-dissolving tablet). In another embodiment,the pharmaceutical composition provides complete buccal and/orsublingual dissolution in about 5 minutes or less (e.g., about 4, 3, 2,1, or 0.5 minutes or less) following administration.

In a further aspect, the present invention provides a solidpharmaceutical composition for delivery across the oral mucosa fortreating insomnia comprising zolpidem in an amount less than 5 mg and abuffer.

Generally, the buffer comprises a carbonate buffer, a bicarbonatebuffer, or a mixture thereof. In certain instances, the buffer is abinary buffer comprising, e.g., a carbonate buffer and a bicarbonatebuffer.

In some embodiments, the amount of zolpidem is less than about 1.30×10⁻⁵moles of zolpidem. In other embodiments, the amount of zolpidem is fromabout 0.5 to about 4.75 mg of zolpidem hemitartrate, e.g., from about1.5 to about 2.5 mg of zolpidem hemitartrate, alternatively from about3.0 to about 3.75 mg of zolpidem hemitartrate, alternatively from about1.0 to about 3.75 mg of zolpidem hemitartrate, or alternatively fromabout 1.5 to about 3.0 mg of zolpidem hemitartrate.

The solid pharmaceutical composition is typically in a dosage formincluding, but not limited to, a lozenge, a chewing gum, a chewabletablet, and a dissolving tablet such as a slow-dissolving tablet or aquick-dissolving tablet. Preferably, the solid pharmaceuticalcomposition is in the form of a lozenge or a quick-dissolving sublingualtablet. The zolpidem is typically delivered across the sublingual and/orbuccal mucosa.

In a related aspect, the present invention provides a solidpharmaceutical composition for delivery across the oral mucosa fortreating insomnia comprising zolpidem in an amount less than about 5 mgand a binary buffer.

In one embodiment, the amount of zolpidem is from about 0.5 to about4.75 mg of zolpidem hemitartrate. Preferably, the amount of zolpidem isfrom about 1.5 to about 2.5 mg of zolpidem hemitartrate, alternativelyfrom about 3.0 to about 3.75 mg of zolpidem hemitartrate, alternativelyfrom about 1.0 to about 3.75 mg of zolpidem hemitartrate, oralternatively from about 1.5 to about 3.0 mg of zolpidem hemitartrate.In certain other instances, the amount of zolpidem is less than about1.30×10⁻⁵ moles of zolpidem.

In some embodiments, the binary buffer comprises a carbonate buffer suchas sodium carbonate and a bicarbonate buffer such as sodium bicarbonate.Preferably, the solid pharmaceutical composition is a lozenge or tabletsuch as a sublingual tablet.

In another related aspect, the present invention provides a solid unitdosage pharmaceutical composition comprising a dose of zolpidemhemitartrate in an amount of less than about 5 mg and a binary buffersystem capable of raising the pH of a subject's saliva to a pH greaterthan about 8.5, alternatively greater than about 9.0, alternativelygreater than about 9.5, alternatively greater than about 10.0,alternatively greater than about 10.5, alternatively greater than about11.0, or alternatively between about 9.0 and about 11.0, irrespective ofthe starting pH of saliva, wherein the composition is formulated fordelivery of zolpidem across the subject's oral mucosa.

In one embodiment, the solid unit dosage pharmaceutical compositioncontains from about 0.5 to about 4.75 mg of zolpidem hemitartrate.Preferably, the solid unit dosage pharmaceutical composition containsfrom about 1.5 to about 2.5 mg of zolpidem hemitartrate, alternativelyfrom about 3.0 to about 3.75 mg of zolpidem hemitartrate, alternativelyfrom about 1.0 to about 3.75 mg of zolpidem hemitartrate, oralternatively from about 1.5 to about 3.0 mg of zolpidem hemitartrate.

In some embodiments, the binary buffer system comprises a carbonate saltsuch as sodium carbonate and a bicarbonate salt such as sodiumbicarbonate. In other embodiments, the binary buffer system comprises acarbonate salt and a bicarbonate salt in a carbonate:bicarbonate ratioof from about 1:1.0 to about 1:1.4 by weight, or alternatively fromabout 1:1.0 to about 1:1.2 by weight.

In an additional aspect, the present invention provides a pharmaceuticalcomposition for treating insomnia comprising zolpidem in an amount lessthan 5 mg and a binary buffer.

The pharmaceutical composition is typically in a dosage form suitablefor delivery of zolpidem across a subject's oral mucosa (e.g., buccaland/or sublingual delivery) including, but not limited to, a lozenge, achewing gum, a chewable tablet, and a dissolving tablet such as aslow-dissolving tablet or a quick-dissolving tablet. In someembodiments, the binary buffer comprises a carbonate buffer such assodium carbonate and a bicarbonate buffer such as sodium bicarbonate.Alternatively, the binary buffer can comprise any combination ofcarbonate salt and bicarbonate salt known in the art.

In a related aspect, the present invention provides a pharmaceuticalcomposition for treating insomnia comprising zolpidem in an amount lessthan 5 mg and a binary buffer, wherein the composition is formulated fordelivery of zolpidem across the oral mucosa (e.g., buccal and/orsublingual mucosa) and the binary buffer produces a saliva pH of atleast about 8.5, alternatively at least about 9.0, alternatively atleast about 9.5, alternatively at least about 10.0, alternatively atleast about 10.5, alternatively at least about 11.0, or alternativelybetween about 9.0 and about 11.0, irrespective of the starting salivapH.

In another aspect, the present invention provides a method of treatinginsomnia, the method comprising:

-   -   administering to a subject who awakens from sleep and desires to        return to sleep within 30 minutes and sleep for less than 5        hours, a single unit dosage composition comprising an effective        amount of zolpidem or a salt thereof, formulated for delivery of        zolpidem across the subject's oral mucosa,

wherein the effective amount is an amount of less than 1.30×10⁻⁵ molesof zolpidem, and is an amount sufficient to produce a plasmaconcentration between about 25 ng/ml and about 50 ng/ml within 20minutes of administration, when evaluated in an appropriate patientpopulation.

In the methods of the present invention, the single unit dosagecomposition is typically administered pro re nata (“as needed”).Preferably, the single unit dosage composition is a lozenge or tablet(e.g., chewable tablet, slow-dissolving tablet, quick-dissolving tablet)formulated for buccal and/or sublingual delivery of zolpidem. In someembodiments, the single unit dosage composition further comprises abinary buffer system that raises the pH of the subject's saliva to a pHgreater than about 8.5, alternatively greater than about 9.0,alternatively greater than about 9.5, alternatively greater than about10.0, alternatively greater than about 10.5, alternatively greater thanabout 11.0, or alternatively between about 9.0 and about 11.0,irrespective of the starting pH of saliva.

In a preferred embodiment, the single unit dosage composition comprisesfrom about 0.5 to about 4.75 mg of zolpidem hemitartrate and a binarybuffer system that raises the pH of the subject's saliva to a pH greaterthan about 8.5, alternatively greater than about 9.0, alternativelygreater than about 9.5, alternatively greater than about 10.0,alternatively greater than about 10.5, alternatively greater than about11.0, or alternatively between about 9.0 and about 11.0, irrespective ofthe starting pH of saliva. In one embodiment, the binary buffer systemcomprises sodium carbonate and sodium bicarbonate.

In a related aspect, the present invention provides a method of treatingMOTN insomnia in a subject, the method comprising:

-   -   administering to the subject a pharmaceutical composition        comprising zolpidem or a salt thereof in an amount of less than        1.30×10⁻⁵ moles of zolpidem,

wherein the administering is on an as-needed basis, and wherein deliveryof zolpidem occurs across the subject's oral mucosa to produce a bloodlevel of zolpidem in the subject between about 25 ng/ml and about 50ng/ml within about 20 minutes of administration and less than 20 ng/mlat a time 4 hours after administration.

In one embodiment, the pharmaceutical composition provides blood (e.g.,plasma) levels of zolpidem in the subject between about 25 ng/ml andabout 50 ng/ml within about 20, 30, or 40 minutes of administration andless than about 20 ng/ml at a time about 2, 3, or 4 hours afteradministration. In another embodiment, the pharmaceutical compositionprovides about 50% of the maximum plasma concentration (C_(max)) ofzolpidem in about 30 minutes or less, alternatively in about 20 minutesor less, or alternatively in about 10 minutes or less, followingadministration. Methods for determining the blood (e.g., plasma) levelof zolpidem in a subject are described above. The delivery of zolpidemtypically occurs across the subject's sublingual and/or buccal mucosa.

In some embodiments, the pharmaceutical composition comprises at leastone pH-adjusting agent. Examples of pH-adjusting agents include, but arenot limited to, carbonate salts, bicarbonate salts, and mixturesthereof. In other embodiments, the pharmaceutical composition comprisesa binary buffer system that raises the pH of the subject's saliva to apH greater than about 8.5, alternatively greater than about 9.0,alternatively greater than about 9.5, alternatively greater than about10.0, alternatively greater than about 10.5, alternatively greater thanabout 11.0, or alternatively between about 9.0 and about 11.0,irrespective of the starting pH of saliva. For example, the binarybuffer system can comprise sodium carbonate and sodium bicarbonate.Alternatively, the binary buffer system can comprise any combination ofcarbonate salt and bicarbonate salt known in the art.

The pharmaceutical composition is typically in the form of a lozenge, achewing gum, a chewable tablet, or a dissolving tablet such as aslow-dissolving tablet or a quick-dissolving tablet (e.g.,quick-dissolving sublingual tablet). In another embodiment, thepharmaceutical composition contains less than about 5 mg of zolpidemhemitartrate. An effective amount of zolpidem to be administered on anas-needed basis according to the methods of the present invention isdescribed above. Preferably, the pharmaceutical composition containsfrom about 0.5 to about 4.75 mg of zolpidem hemitartrate, alternativelyfrom about 1.5 to about 2.5 mg of zolpidem hemitartrate, oralternatively from about 3.0 to about 3.75 mg of zolpidem hemitartrate.In certain instances, the pharmaceutical composition comprises less thana 5 mg dose of zolpidem hemitartrate and a binary buffer systemconsisting of a carbonate salt and a bicarbonate salt.

In yet another aspect, the present invention provides a method oftreating insomnia in a subject, the method comprising:

-   -   administering to the subject a pharmaceutical composition        comprising zolpidem or a salt thereof,

wherein the composition provides delivery of zolpidem across thesubject's oral mucosa, wherein the subject is a subject who awakens fromsleep and desires to resume sleep for less than 5 hours, and wherein thecomposition produces sleep within 30 minutes of dosing and the dose issuch that it does not produce residual sedative effects when the subjectis awakened at a time 4 hours after dosing.

In one embodiment, the pharmaceutical composition produces sleep withinabout 20, 30, or 40 minutes of dosing but does not produce residualsedative effects when the subject is awakened at a time about 2, 3, or 4hours after dosing. In certain instances, the pharmaceutical compositionproduces polysomnography stage 1 sleep at the onset of sleep.

In another embodiment, the pharmaceutical composition produces blood(e.g., plasma) levels of zolpidem in the subject between about 25 ng/mland about 50 ng/ml within about 20, 30, or 40 minutes of administrationand/or less than about 20 ng/ml at a time about 2, 3, or 4 hours afteradministration. In yet another embodiment, the pharmaceuticalcomposition provides about 50% of the maximum plasma concentration(C_(max)) of zolpidem in about 30 minutes or less, alternatively inabout 20 minutes or less, or alternatively in about 10 minutes or less,following administration. The zolpidem is typically delivered across thesubject's sublingual and/or buccal mucosa.

In some embodiments, the pharmaceutical composition further comprises atleast one pH-adjusting agent. In other embodiments, the pharmaceuticalcomposition further comprises a binary buffer system that raises the pHof the subject's saliva to a pH greater than about 8.5, alternativelygreater than about 9.0, alternatively greater than about 9.5,alternatively greater than about 10.0, alternatively greater than about10.5, alternatively greater than about 11.0, or alternatively betweenabout 9.0 and about 11.0, irrespective of the starting pH of saliva.Preferably, the pharmaceutical composition comprises zolpidemhemitartrate, e.g., in an amount of less than about 5 mg. In certaininstances, the pharmaceutical composition comprises from about 0.5 toabout 4.75 mg of zolpidem hemitartrate, e.g., from about 1.5 to about2.5 mg of zolpidem hemitartrate, alternatively from about 3.0 to about3.75 mg of zolpidem hemitartrate, alternatively from about 1.0 to about3.75 mg of zolpidem hemitartrate, or alternatively from about 1.5 toabout 3.0 mg of zolpidem hemitartrate.

In a preferred embodiment, the pharmaceutical composition comprises fromabout 1.5 to about 2.5 mg of zolpidem hemitartrate or from about 3.0 toabout 3.75 mg of zolpidem hemitartrate and a binary buffer systemconsisting of sodium carbonate and sodium bicarbonate.

The pharmaceutical composition is typically in a solid unit dosage formincluding, but not limited to, a lozenge, a chewing gum, a chewabletablet, and a dissolving tablet such as a slow-dissolving tablet or aquick-dissolving tablet. Preferably, the pharmaceutical composition isin the form of a lozenge or a quick-dissolving sublingual tablet.

In a further aspect, the present invention provides a method of treatinginsomnia in a subject, the method comprising:

-   -   administering a solid pharmaceutical composition comprising        zolpidem in an amount less than 5 mg and a buffer, to a subject        who awakens from sleep and desires to resume sleep for less than        5 hours,

wherein the solid pharmaceutical composition provides delivery ofzolpidem across the subject's oral mucosa, and wherein a blood level ofzolpidem is achieved in the subject of between about 25 ng/ml and about50 ng/ml within about 20 minutes of administration.

In a related aspect, the present invention provides a method of treatinginsomnia, the method comprising the steps of:

-   -   providing a solid pharmaceutical composition comprising zolpidem        in an amount less than 5 mg and a buffer to a patient who        awakens from sleep and desires to resume sleep for less than 5        hours; and    -   administering the solid pharmaceutical composition to the        patient for delivery of the zolpidem across the patient's oral        mucosa,

wherein a blood level of zolpidem in the patient is between about 25ng/ml and about 50 ng/ml within about 20 minutes of administration.

In one embodiment, the solid pharmaceutical composition achieves a blood(e.g., plasma) level of zolpidem in the subject between about 25 ng/mland about 50 ng/ml within about 20, 30, or 40 minutes of administration.In another embodiment, the solid pharmaceutical composition provides ablood level of zolpidem in the subject less than about 20 ng/ml withinabout 2, 3, or 4 hours of administration.

In some embodiments, the solid pharmaceutical composition dissolves ordisintegrates in the subject's mouth in about 2 minutes or less (e.g.,about 2, 1.5, 1, or 0.5 minutes or less). In other embodiments, thesolid pharmaceutical composition dissolves or disintegrates in thesubject's mouth in about 3 to about 6 minutes (e.g., about 3, 3.5, 4,4.5, 5, 5.5, or 6 minutes). The zolpidem is typically delivered acrossthe subject's sublingual and/or buccal mucosa.

Generally, the buffer that is present in the pharmaceutical compositionraises the pH of saliva in the subject's mouth to a pH greater thanabout 8.5, alternatively greater than about 9.0, alternatively greaterthan about 9.5, alternatively greater than about 10.0, alternativelygreater than about 10.5, alternatively greater than about 11.0, oralternatively between about 9.0 and about 11.0, irrespective of thestarting pH of saliva. Preferably, the pH of the saliva is raised aboveabout 9.0 for at least about 2 minutes (e.g., about 2, 2.5, 3, 3.5, 4,4.5, 5, 5.5, 6, or more minutes). In certain instances, the buffer is abinary buffer. A non-limiting example of a suitable binary bufferincludes a mixture of a carbonate buffer and a bicarbonate buffer.

In an additional aspect, the present invention provides a method oftreating insomnia, the method comprising:

-   -   administering a solid pharmaceutical composition comprising        zolpidem in an amount less than 5 mg and a binary buffer, to a        subject who awakens from sleep and desires to resume sleep for        less than 5 hours,

wherein the solid pharmaceutical composition provides delivery ofzolpidem across the subject's oral mucosa, wherein the solidpharmaceutical composition dissolves or disintegrates in about 2 minutesor less in the subject's mouth, and wherein the binary buffer raises thepH of saliva in the subject's mouth to a pH greater than about 9.0.

In a related aspect, the present invention provides a method of treatinginsomnia, the method comprising the steps of:

-   -   providing a solid pharmaceutical composition comprising zolpidem        in an amount less than 5 mg and a binary buffer to a patient who        awakens from sleep and desires to resume sleep for less than 5        hours; and    -   administering the solid pharmaceutical composition to the        patient for delivery of the zolpidem across the patient's oral        mucosa,

wherein the solid pharmaceutical composition dissolves or disintegratesin about 2 minutes or less in the patient's mouth, and wherein thebinary buffer raises the pH of saliva in the patient's mouth to a pHgreater than about 9.0.

In one embodiment, the solid pharmaceutical composition achieves a blood(e.g., plasma) level of zolpidem in the subject between about 25 ng/mland about 50 ng/ml within about 20, 30, or 40 minutes of administration.In another embodiment, the solid pharmaceutical composition provides ablood level of zolpidem in the subject less than about 20 ng/ml withinabout 2, 3, or 4 hours of administration.

In some embodiments, the pH of the saliva is raised above about 9.0 forat least about 2 minutes (e.g., 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, ormore minutes). In other embodiments, the binary buffer comprises acarbonate buffer and a bicarbonate buffer. The zolpidem is typicallydelivered across the subject's sublingual and/or buccal mucosa.

IV. Compositions

Typically, the compositions of the present invention will containzolpidem or a salt thereof in an amount of about 0.5 mg, about 0.8 mg,about 1.0 mg, about 1.5 mg, about 1.75 mg, about 2.0 mg, about 2.5 mg,about 3.0 mg, about 3.5 mg, about 3.75 mg, about 4.0 mg, about 4.5 mg,or about 4.75 mg per administration. However, the amount of zolpidem canbe any dose amount less than about 5 mg, alternatively from about 1.5 toabout 2.5 mg, or alternatively from about 3.0 to about 3.75 mg. Oneskilled in the art will appreciate that the amount of zolpidem can beexpressed as the number of moles of zolpidem present in the composition.For example, 5 mg of zolpidem hemitartrate is equivalent to about1.30×10⁻⁵ moles of zolpidem. As such, in some embodiments, thecomposition will contain an amount of zolpidem hemitartrate thatprovides less than about 1.30×10⁻⁵ moles of zolpidem.

Any form of zolpidem is suitable for use in the compositions describedherein, e.g., a salt form of zolpidem, a free base form of zolpidem, apolymorph of zolpidem, or a mixture thereof. For example,pharmaceutically acceptable salts of zolpidem can include, withoutlimitation, tartrate, hemitartrate, succinate, dihydrochloride,salicylate, hemisuccinate, citrate, maleate, hydrochloride, carbamate,sulfate, nitrate, and benzoate salt forms, as well as combinationsthereof. In some embodiments, the zolpidem is in the form of a salt,e.g., zolpidem hemitartrate. In other embodiments, the zolpidem is inthe form of a polymorph, e.g., commercially available from Plantex Ltd.(Netanya, Israel).

The compositions of the present invention may take the form of solid,semi-solid, lyophilized powder, or liquid dosage forms, such as, forexample, tablets (e.g., chewable, slow-dissolving, quick-dissolving,etc.), pills, capsules, lozenges, gums, powders, solutions, suspensions,emulsions, aerosols, foams, creams, gels, lotions, or the like.Preferably, the compositions of the present invention are formulated asa tablet or a lozenge, in particular quick-dissolving tablets orlozenges, such as those described in U.S. Patent Publication No.20050226925.

As used herein, the term “unit dosage” or “dosage form” refers tophysically discrete units suitable as unitary dosages for human subjectsand other mammals, each unit containing a predetermined quantity oftherapeutic agent calculated to produce the desired onset, tolerability,and therapeutic effects, in association with one or more suitablepharmaceutical excipients such as carriers. Methods for preparing suchdosage forms are known or will be apparent to those skilled in the art.For example, in some embodiments, a chewing gum dosage form of thepresent invention can be prepared according to the procedures set forthin U.S. Pat. No. 4,405,647. In other embodiments, a liquid spray or asolution, tincture, tablet, lozenge, or candy dosage form of the presentinvention can be prepared according to the procedures set forth, forexample, in Remington: The Science and Practice of Pharmacy, 20^(th)Ed., Lippincott, Williams & Wilkins (2003); Pharmaceutical Dosage Forms,Volume 1: Tablets, 2^(nd) Ed., Marcel Dekker, Inc., New York, N.Y.(1989); and similar publications. The dosage form to be administeredwill, in any event, contain a quantity of the therapeutic agent in atherapeutically effective amount for relief of the condition beingtreated when administered in accordance with the teachings of thepresent invention.

The terms “carrier” or “excipient” refer to a typically inert substanceused as a diluent or vehicle for a drug such as a therapeutic agent. Theterm also encompasses a typically inert substance that imparts cohesivequalities to the composition. Suitable carriers for use in thecompositions of the present invention include, without limitation, abinder, a gum base, and combinations thereof. Non-limiting examples ofbinders include mannitol, sorbitol, xylitol, maltodextrin, lactose,dextrose, sucrose, glucose, inositol, powdered sugar, molasses, starch,cellulose, microcrystalline cellulose, polyvinylpyrrolidone, acacia gum,guar gum, tragacanth gum, alginate, extract of Irish moss, panwar gum,ghatti gum, mucilage of isapol husks, Veegum®, larch arabogalactan,gelatin, methylcellulose, ethylcellulose, carboxymethylcellulose,hydroxypropylmethylcellulose, polyoxyethylene polymers, polyacrylic acid(e.g., Carbopol), calcium silicate, calcium phosphate, dicalciumphosphate, calcium sulfate, kaolin, sodium chloride, polyethyleneglycol, propylene glycol, and combinations thereof. These binders can bepre-processed to improve their flowability and taste by methods known inthe art such as freeze drying (see, e.g., Fundamentals of Freeze-Drying,Pharm. Biotechnol., 14:281-360 (2002); Lyophililization of Unit DosePharmaceutical Dosage Forms, Drug. Dev. Ind. Pharm., 29:595-602 (2003));solid-solution preparation (see, e.g., U.S. Pat. No. 6,264,987); andlubricant dusting and wet-granulation preparation with a suitablelubricating agent (see, e.g., Remington: The Science and Practice ofPharmacy, supra). For example, Mannogem® and Sorbogem®, sold by SPIPharma Group (New Castle, Del.), are freeze-dried processed forms ofmannitol and sorbitol, respectively. Typically, the compositions of thepresent invention comprise from about 25% to about 90% by weight of thebinder, and preferably from about 50% to about 80%. However, one skilledin the art will appreciate that the compositions of the presentinvention can be made without any binders, e.g., to produce a highlyfriable dosage form.

Non-limiting examples of gum bases include materials selected from amongthe many water-insoluble and saliva-insoluble gum base materials knownin the art. For example, in some instances, the gum base comprises atleast one hydrophobic polymer and at least one hydrophilic polymer.Non-limiting examples of suitable hydrophobic and hydrophilic polymersfor gum bases include both natural and synthetic polymers such aselastomers, rubbers, and combinations thereof. Examples of suitablenatural polymers include, without limitation, substances of plant originsuch as chicle, jelutong, gutta percha, crown gum, and combinationsthereof. Examples of suitable synthetic polymers include elastomers suchas butadiene-styrene copolymers, isobutylene and isoprene copolymers(e.g., “butyl rubber”), polyethylene, polyisobutylene, polyvinylester(e.g., polyvinyl acetate and polyvinyl acetate phthalate), andcombinations thereof. In other instances, the gum base comprises amixture of butyl rubber (i.e., isobutylene and isoprene copolymer),polyisobutylene, and optionally, polyvinylacetate (e.g., having amolecular weight of approximately 12,000). Typically, the gum basecomprises from about 25% to about 75% by weight of these polymers, andpreferably from about 30% to about 60%.

The compositions of the present invention can additionally includelubricating agents; wetting agents; emulsifying agents; solubilizingagents; suspending agents; preserving agents such as methyl-, ethyl-,and propyl-hydroxy-benzoates, butylated hydroxytoluene, and butylatedhydroxyanisole; sweetening agents; flavoring agents; coloring agents;and disintegrating agents such as crospovidone as well as croscarmellosesodium and other cross-linked cellulose polymers.

Lubricating agents can be used to prevent adhesion of the dosage form tothe surface of the dies and punches, and to reduce inter-particlefriction. Lubricating agents may also facilitate ejection of the dosageform from the die cavity and improve the rate of granulation flow duringprocessing. Examples of suitable lubricating agents include, withoutlimitation, magnesium stearate, calcium stearate, zinc stearate, stearicacid, sodium stearyl fumarate, simethicone, silicon dioxide, talc,hydrogenated vegetable oil, polyethylene glycol, mineral oil, andcombinations thereof. The compositions of the present invention cancomprise from about 0% to about 10% by weight of the lubricating agent,and preferably from about 1% to about 5%.

Sweetening agents can be used to improve the palatability of thecomposition by masking any unpleasant tastes it may have. Examples ofsuitable sweetening agents include, without limitation, compoundsselected from the saccharide family such as the mono-, di-, tri-, poly-,and oligosaccharides; sugars such as sucrose, glucose (corn syrup),dextrose, invert sugar, fructose, maltodextrin, and polydextrose;saccharin and salts thereof such as sodium and calcium salts; cyclamicacid and salts thereof; dipeptide sweeteners; chlorinated sugarderivatives such as sucralose and dihydrochalcone; sugar alcohols suchas sorbitol, sorbitol syrup, mannitol, xylitol, hexa-resorcinol, and thelike, and combinations thereof. Hydrogenated starch hydrolysate, and thepotassium, calcium, and sodium salts of3,6-dihydro-6-methyl-1-1,2,3-oxathiazin-4-one-2,2-dioxide may also beused. Of the foregoing, sorbitol, mannitol, and xylitol, either alone orin combination, are preferred sweetening agents. The compositions of thepresent invention can comprise from about 0% to about 80% by weight ofthe sweetening agent, preferably from about 5% to about 75%, and morepreferably from about 25% to about 50%.

Flavoring agents can also be used to improve the palatability of thecomposition. Examples of suitable flavoring agents include, withoutlimitation, natural and/or synthetic (i.e., artificial) compounds suchas peppermint, spearmint, wintergreen, cinnamon, menthol, cherry,strawberry, watermelon, grape, banana, peach, pineapple, apricot, pear,raspberry, lemon, grapefruit, orange, plum, apple, fruit punch, passionfruit, chocolate (e.g., white, milk, dark), vanilla, caramel, coffee,hazelnut, combinations thereof, and the like. Coloring agents can beused to color code the composition, for example, to indicate the typeand dosage of the therapeutic agent therein. Suitable coloring agentsinclude, without limitation, natural and/or artificial compounds such asFD & C coloring agents, natural juice concentrates, pigments such astitanium oxide, silicon dioxide, and zinc oxide, combinations thereof,and the like. The compositions of the present invention can comprisefrom about 0% to about 10% by weight of the flavoring and/or coloringagent, preferably from about 0.1% to about 5%, and more preferably fromabout 2% to about 3%.

When the dosage form is a chewing gum, the composition can comprisezolpidem or a pharmaceutically acceptable salt thereof (“therapeuticagent”), a carrier or excipient such as a gum base, a pH-adjusting agentor buffer system, and optionally a protecting agent. The chewing gumcomposition may further comprise lubricating agents, wetting agents,emulsifying agents, solubilizing agents; suspending agents, preservingagents, sweetening agents, flavoring agents, and coloring agents.Typically, the chewing gum composition comprises less than about 5 mg(e.g., from about 0.5 mg to about 4.75 mg, from about 1.5 mg to about2.5 mg, from about 3.0 mg to about 3.75 mg, etc.) of zolpidem or a saltthereof. One skilled in the art understands that the foregoing amountswill vary depending upon the particular source of zolpidem utilized, theamount of zolpidem desired in the final formulation, as well as on theparticular release rate of zolpidem desired. In certain instances, thebuffer system of the chewing gum composition provides a final salivarypH in excess of at least about 7.8, preferably at least about 8.5, andmore preferably at least about 9 (e.g., about 9-11). The chewing gumcomposition typically comprises from about 20% to about 95% by weight ofthe gum base, more typically from about 30% to about 85%, and mosttypically from about 50% to about 70% of the gum base.

The chewing gum composition may further comprise a protecting agent. Theprotecting agent coats at least part of the therapeutic agent, typicallyupon the mixing of the two agents. The protecting agent may be mixedwith the therapeutic agent in a ratio of from about 0.1 to about 100 byweight, preferably in a ratio of from about 1 to about 50, and morepreferably in a ratio of from about 1 to about 10. Without being boundto any particular theory, the protecting agent reduces the adhesionbetween the therapeutic agent and the gum base so that the therapeuticagent may be more easily released from the gum base. In this way, thetherapeutic agent may be delivered across the mucous membranes of theoral cavity within about 5 to about 20 minutes of chewing, preferablywithin about 10 minutes of chewing. A variety of different protectingagents may be used. Examples of suitable protecting agents include,without limitation, calcium stearate, glycerin monostearate, glycerylbehenate, glyceryl palmitostearate, hydrogenated castor oil,hydrogenated vegetable oil type I, light mineral oil, magnesium laurylsulfate, magnesium stearate, sodium stearyl fumarate, mineral oil,poloxamer, polyethylene gycol, sodium benzoate, sodium chloride, sodiumlauryl sulfate, stearic acid, cab-o-sil, talc, zinc stearate, andcombinations thereof.

The gum base may additionally include plasticizers such as softeners oremulsifiers. Such plasticizers may, for example, help reduce theviscosity of the gum base to a desirable consistency and improve itsoverall texture and bite. Plasticizers may also facilitate the releaseof the therapeutic agent upon mastication. Non-limiting examples ofplasticizers include lecithin, mono- and diglycerides, lanolin, stearicacid, sodium stearate, potassium stearate, glycerol triacetate, glycerolmonostearate, glycerin, and combinations thereof. The gum base typicallycomprises from about 0% to about 20% by weight of the plasticizer, andmore typically from about 5% to about 15%.

The gum base may further comprise waxes such as beeswax andmicrocrystalline wax, fats or oils such as soybean and cottonseed oil,and combinations thereof. Typically, the gum base comprises from about0% to about 25% by weight of these waxes and oils, and more typicallycomprises from about 15% to about 20%.

In addition, the gum base may further comprise one or more elastomericsolvents such as rosins and resins. Non-limiting examples of suchsolvents include methyl, glycerol, and pentaerythritol esters of rosins,modified rosins such as hydrogenated, dimerized or polymerized rosins,or combinations thereof (e.g., pentaerythritol ester of partiallyhydrogenated wood rosin, pentaerythritol ester of wood rosin, glycerolester of wood rosin, glycerol ester of partially dimerized rosin,glycerol ester of polymerized rosin, glycerol ester of tall oil rosin,glycerol ester of wood rosin and partially hydrogenated wood rosin andpartially hydrogenated methyl ester of rosin such as polymers ofalpha-pinene or beta-pinene, terpene resins including polyterpene, andcombinations thereof). Typically, the gum base comprises from about 0%to about 75% by weight of the elastomeric solvent, and more typicallyless than about 10%.

The gum base may further comprise a filler material to enhance thechewability of the final chewing gum composition. Fillers that aresubstantially non-reactive with other components of the final chewinggum formulation are preferable. Examples of suitable fillers include,without limitation, calcium carbonate, magnesium silicate (i.e., talc),dicalcium phosphate, metallic mineral salts (e.g., alumina, aluminumhydroxide, and aluminum silicates), and combinations thereof. Typically,the gum base comprises from about 0% to about 30% by weight of thefiller, and more typically from about 10% to about 20%.

One skilled in the art will appreciate that the gum base need not beprepared from its individual components. For example, the gum base canbe purchased with the desired ingredients contained therein, and can bemodified to include additional agents. Several manufacturers produce gumbases suitable for use with the described chewing gum compositions.Examples of such gum bases include, without limitation, Pharmagum™M, S,or C(SPI Pharma Group; New Castle, Del.). In general, Pharmagum™comprises a mixture of gum base, sweetening agent, plasticizer, andsugar.

In certain instances, the chewing gum composition includes a therapeuticagent centerfill. A centerfill may be particularly suitable whenimmediate release of the therapeutic agent is preferred. In addition,encapsulating the therapeutic agent in a centerfill may help to mask anyundesirable taste that the therapeutic agent may have. In theseinstances, the gum base surrounds, at least in part, a centerfill. Thecenterfill comprises at least one therapeutic agent, and may be a liquidor semi-liquid material. The centerfill material can be a syntheticpolymer, a semi-synthetic polymer, low-fat, or fat-free and contain oneor more sweetening agents, flavoring agents, coloring agents, and/orscenting agents. Preferably, the centerfill includes a buffer system asdescribed herein. Methods for preparing a centerfill chewing gum aredescribed, for example, in U.S. Pat. No. 3,806,290.

The chewing gum compositions can have any desired shape, size, andtexture. For example, the chewing gum can have the shape of a stick,tab, gumball, and the like. Similarly, the chewing gum can be anydesirable color. For example, the chewing gum can be any shade of red,blue, green, orange, yellow, violet, indigo, and mixtures thereof, andcan be color coded to indicate the type and dosage of the therapeuticagent therein. The chewing gum can be individually wrapped or groupedtogether in pieces for packaging by methods well known in the art.

When the dosage form is a tablet such as a dissolving tablet or chewabletablet, the composition can comprise zolpidem or a pharmaceuticallyacceptable salt thereof, a carrier or excipient such as a binder, and apH-adjusting agent or buffer system. The tablet composition may furthercomprise protecting agents, lubricating agents, wetting agents,emulsifying agents, solubilizing agents; suspending agents, preservingagents, sweetening agents, flavoring agents, coloring agents, anddisintegrating agents. Typically, the tablet compositions of the presentinvention comprise less than about 5 mg (e.g., from about 0.5 mg toabout 4.75 mg, from about 1.5 mg to about 2.5 mg, from about 3.0 mg toabout 3.75 mg, etc.) of zolpidem or a salt thereof. One skilled in theart understands that the foregoing amounts will vary depending upon theparticular source of zolpidem utilized, the amount of zolpidem desiredin the final formulation, as well as on the particular release rate ofzolpidem desired. In certain instances, the buffer system of the tabletcompositions provide a final salivary pH in excess of at least about7.8, preferably at least about 8.5, and more preferably at least about 9(e.g., about 9-11).

In certain embodiments, the tablet is a dissolving tablet such as aslow-dissolving or quick-dissolving tablet that is dissolved by asubject's saliva, without the need for chewing. For example, adissolving tablet placed on the subject's tongue can be used for buccaldelivery of the therapeutic agent. Alternatively, a dissolving tabletplaced underneath the subject's tongue can be used for sublingualdelivery of the therapeutic agent. This type of dosage form may beparticularly desirable for pediatric and geriatric patients, since smallchildren and aged individuals often have difficulty chewing certainitems. Typically, the dissolving tablet is formulated to dissolve withinabout 1 to about 15 minutes, preferably within about 2 to about 10minutes, e.g., within about 2, 3, 4, 5, 6, 7, 8, 9, or 10 minutes,following administration. One skilled in the art will understand thatquick-dissolving tablets dissolve faster than slow-dissolving tablets,which are typically dissolved gradually rather than rapidly by asubject's saliva. In a preferred embodiment, the slow-dissolving orquick-dissolving tablet delivers the therapeutic agent across thesublingual mucosa.

In certain other embodiments, the tablet is a chewable tablet that ischewed by a subject and formulated to dissolve either rapidly orgradually. For example, a chewable tablet placed on the subject's tonguecan be used for buccal delivery of the therapeutic agent. Duringchewing, the chewable tablet can be moved around within the mouth andcan sometimes be parked between the gums and the cheeks or underneaththe tongue. As a result, at least a portion of the therapeutic agentcontained within a chewable tablet may also be delivered sublingually(i.e., across the sublingual mucosa). Typically, the chewable tablet isformulated to dissolve within about 1 to about 15 minutes, preferablywithin about 2 to about 10 minutes, e.g., within about 2, 3, 4, 5, 6, 7,8, 9, or 10 minutes, following administration.

As described above, the dissolving and chewable tablets of the presentinvention are typically formulated to dissolve within about 1 to about15 minutes following administration. However, while these time framesare amenable to maximum exposure of the therapeutic agent to the oralmucosa (e.g., to the sublingual and/or buccal mucosa), they are notalways amenable to user compliance (e.g., users may swallow toofrequently and, therefore, hinder maximal transmucosal absorption).Consequently, in certain instances, it may be desirable to strike abalance between patient compliance and maximum exposure time of thetherapeutic agent to the oral mucosa. This can be accomplished, forexample, by reducing the tablet size (e.g., from about 700-800 mg toabout 200-300 mg or about 100-350 mg) without reducing the concentrationor amount per unit dose of the buffer system or the therapeutic agent.In addition, subtle changes to the tablet formulation such as, forexample, replacing one flavoring agent for another (e.g., chocolate forspearmint) or replacing one binder or sweetening agent for another(e.g., lactose for mannitol or sorbitol) may be used to reducesalivation.

The carrier or excipient present in the tablets of the present inventionis typically a binder that is useful in keeping the tablet in asemi-solid state, and may be a solid or a liquid, and may for example bea high-melting point fat or waxy material. Materials suitable as bindersare discussed in detail above and may be used alone or in combination inthe tablet compositions of the present invention. In addition, binderssuch as mannitol, sorbitol, lactose, sucrose, and inositol can impartproperties to the tablet that permit or enhance its disintegration inthe mouth.

The tablet composition may also comprise one or more elastomericsolvents such as rosins and resins. Non-limiting examples of suchsolvents are discussed in detail above and may be used alone or incombination in the tablet compositions of the present invention. Inaddition, the tablet composition may further comprise waxes such asbeeswax and microcrystalline wax, fats or oils such as soybean andcottonseed oil, and combinations thereof. Moreover, the tabletcomposition may additionally include plasticizers such as softeners oremulsifiers. Such plasticizers may, for example, help reduce theviscosity of the salivary solution of the dissolved tablet to adesirable consistency and improve its overall texture and bite and helpfacilitate the release of the therapeutic agent. Non-limiting examplesof such plasticizers are discussed in detail above and may be used aloneor in combination in the tablet compositions of the present invention.

In certain instances, the tablet composition includes a therapeuticagent centerfill, e.g., as described above. In certain other instances,the tablet composition of the present invention is multilayered. In thisway, the dissolving or chewable tablet can be designed to provide morethan one therapeutic agent. For example, with a bi-layered tablet, thefirst layer can contain zolpidem or a salt thereof and the second layercan contain the same or different hypnotic agent or a non-hypnoticagent. Typically, the first layer comprises the dissolving or chewableportion of the tablet, and the second (i.e., subsequent) layer is coatedby the first layer. This type of formulation may be particularlysuitable when immediate release of zolpidem, followed bygastrointestinal absorption of a second therapeutic agent, is desirable.Gastrointestinal absorption of the second therapeutic agent may bedesirable, for example, in order to mitigate co-morbid symptoms or tosustain the therapeutic benefit of zolpidem in the dissolving or thechewable portion of the tablet. Alternatively, the second layer ispresent as a layer lateral to the first layer. The second layertypically comprises at least one therapeutic agent, and can alsocomprise one or more sweetening agents, flavoring agents, coloringagents, and scenting agents as described above. In some instances, thesecond layer further includes a buffer system as described herein.

In still other instances, the combination of zolpidem or a salt thereofwith other hypnotic agents and/or non-hypnotic agents need not take theform of a multilayered tablet, but instead comprises a single homogenoustablet layer. This type of formulation may also be used in the casewhere gastrointestinal absorption of at least one therapeutic agent isdesirable. In this case, the relative extent of ionization of the two ormore therapeutic agents determines how they are to be absorbed. Forexample, those therapeutic agents that are un-ionized are absorbedthrough the oral mucosa, while the ionized agents are swallowed forgastrointestinal absorption.

The tablet compositions can have any desired shape, size, and texture.For example, the tablet can have the shape of a stick, tab, pellet,sphere, and the like. Similarly, the tablet can be any desirable color.For example, the tablet can be any shade of red, blue, green, orange,yellow, violet, indigo, and mixtures thereof, and can be color coded toindicate the type and dosage of the therapeutic agent therein. Thetablets can be individually wrapped or grouped together in pieces forpackaging by methods well known in the art.

When the dosage form is a lozenge or candy, the composition can comprisezolpidem or a pharmaceutically acceptable salt thereof, a carrier orexcipient such as a binder, and a pH-adjusting agent or buffer system.The lozenge or candy composition may further comprise protecting agents,lubricating agents, wetting agents, emulsifying agents, solubilizingagents; suspending agents, preserving agents, sweetening agents,flavoring agents, coloring agents, and disintegrating agents. A generaldiscussion of lozenges and candies is provided, e.g., in PharmaceuticalDosage Forms, Volume 1: Tablets, 2^(nd) Ed., Marcel Dekker, Inc., NewYork, N.Y., pages 75-418 (1989). Typically, the lozenge compositions ofthe present invention comprise less than about 5 mg (e.g., from about0.5 mg to about 4.75 mg, from about 1.5 mg to about 2.5 mg, from about3.0 mg to about 3.75 mg, etc.) of zolpidem or a salt thereof. Oneskilled in the art understands that the foregoing amounts will varydepending upon the particular source of zolpidem utilized, the amount ofzolpidem desired in the final formulation, as well as on the particularrelease rate of zolpidem desired. In certain instances, the buffersystem of the lozenge compositions provides a final salivary pH inexcess of at least about 7.8, preferably at least about 8.5, and morepreferably at least about 9 (e.g., about 9-11).

In certain embodiments, the lozenge or candy is dissolved by a subject'ssaliva, without the need for chewing. For example, a lozenge placed onthe subject's tongue can be used for buccal delivery of the therapeuticagent. Alternatively, a lozenge placed underneath the subject's tonguecan be used for sublingual delivery of the therapeutic agent. This typeof dosage form may be particularly desirable for pediatric and geriatricpatients, since small children and aged individuals often havedifficulty chewing certain items. Typically, the lozenge is formulatedto dissolve within about 1 to about 15 minutes, preferably within about2 to about 10 minutes, e.g., within about 2, 3, 4, 5, 6, 7, 8, 9, or 10minutes, following administration. In a preferred embodiment, thelozenge or candy delivers the therapeutic agent across the sublingualmucosa.

As described above, the lozenges the present invention are typicallyformulated to dissolve within about 1 to about 15 minutes followingadministration. However, while these time frames are amenable to maximumexposure of the therapeutic agent to the oral mucosa (e.g., to thesublingual and/or buccal mucosa), they are not always amenable to usercompliance (e.g., users may swallow too frequently and, therefore,hinder maximal transmucosal absorption). Consequently, in certaininstances, it may be desirable to strike a balance between patientcompliance and maximum exposure time of the therapeutic agent to theoral mucosa. This can be accomplished, for example, by reducing thelozenge size (e.g., from about 700-800 mg to about 200-300 mg or about100-350 mg) without reducing the concentration or amount per unit doseof the buffer system or the therapeutic agent. In addition, subtlechanges to the lozenge formulation such as, for example, replacing oneflavoring agent for another (e.g., chocolate for spearmint) or replacingone binder or sweetening agent for another (e.g., lactose for mannitolor sorbitol) may be used to reduce salivation.

The carrier or excipient present in the lozenges of the presentinvention is typically a binder that is useful in keeping the lozenge ina semi-solid state, and may be a solid or a liquid, and may for examplebe a high-melting point fat or waxy material. Materials suitable asbinders are discussed in detail above and may be used alone or incombination in the lozenge compositions of the present invention. Inaddition, binders such as mannitol, sorbitol, lactose, sucrose, andinositol can impart properties to the lozenge that permit or enhance itsdisintegration in the mouth.

The lozenge composition may also comprise one or more elastomericsolvents such as rosins and resins. Non-limiting examples of suchsolvents are discussed in detail above and may be used alone or incombination in the lozenge compositions of the present invention. Inaddition, the lozenge composition may further comprise waxes such asbeeswax and microcrystalline wax, fats, or oils such as soybean andcottonseed oil, and combinations thereof. Moreover, the lozengecomposition may additionally include plasticizers such as softeners oremulsifiers. Such plasticizers may, for example, help reduce theviscosity of the salivary solution of the dissolved lozenge to adesirable consistency and improve its overall texture and bite and helpfacilitate the release of the therapeutic agent. Non-limiting examplesof such plasticizers are discussed in detail above and may be used aloneor in combination in the lozenge compositions of the present invention.

In other embodiments, the lozenge composition includes a therapeuticagent centerfill, is multilayered, or comprises a single homogenouslozenge layer, e.g., as described in detail above.

The lozenge compositions can have any desired shape, size, and texture.For example, the lozenge can have the shape of a stick, tab, pellet,sphere, and the like. Similarly, the lozenge can be any desirable color.For example, the lozenge can be any shade of red, blue, green, orange,yellow, violet, indigo, and mixtures thereof, and can be color coded toindicate the type and dosage of the therapeutic agent therein. Thelozenges can be individually wrapped or grouped together in pieces forpackaging by methods well known in the art.

In a preferred embodiment, the average particle size of the drug in thecompositions described herein is about 20 microns, as compared to atypical average drug particle size of from about 75 to about 100microns. In another preferred embodiment, the average particle size ofthe drug in the compositions described herein is less than or equal tothe average particle size of the carrier ingredients (e.g., gum base,binders, etc.).

Typically, the pharmaceutical compositions are suitable for buccal orsublingual administration of zolpidem in the low doses provided herein.Compositions suitable for buccal or sublingual administration ofzolpidem are those that provide absorption in the buccal cavity of atleast about 10%, 20%, or 25% of the dosage of zolpidem in thecomposition. This amount is generally at least twice the amount ofbuccal absorption that could be expected for a tablet designed to beswallowed for absorption of the active agent in the gut. Additionally,the time to C_(max) is reduced for such compositions relative to tabletsor capsules designed to deliver zolpidem in the gut. The compositionssuitable for buccal or sublingual administration of zolpidem in lowdoses, as noted above, are sufficient to reduce the time to C_(max)enhancing the early effect of zolpidem and increase plasma levels ofzolpidem, generally two-fold or more during the first 20 minutes afteradministration, relative to tablets or capsules designed for delivery inthe gut (e.g., to be swallowed immediately upon ingestion).

Typically, the compositions that are suitable for the treatment of MOTNinsomnia following buccal or sublingual administration have a unique anddiscriminatory dissolution profile. Such a dissolution method relies onmodified USP method II dissolution procedure and where the pH of thedissolution medium is 6.8, which approximates the pH of the saliva. Themethod is considered to be a modification as the volume of the medium isreduced to 500 ml from 1 liter and the paddle speed for dissolution isreduced to 15 rpm from a typical speed of 50 or more rpm. This method issufficiently sensitive to discriminate a 2 to 3 minute dissolutiontablet from a tablet that would normally take 5 minutes or more todissolve in the mouth. Typically, a tablet that would dissolve in themouth in 3 minutes or less would dissolve more rapidly underexperimental conditions of modified USP method II than a tablet thattakes 5 or more minutes to dissolve in the mouth (see, Tables 1-2 below)TABLE 1 Exploratory dissolution profiles of 3 and 5 minute dissolutionof zolpidem lozenges using the modified USP dissolution method II. (500ml of pH 6.8 phosphate buffer at a 37° C. and paddle speed of 15 rpm).“3 minute” “5 minute” Lozenge dissolution prototype dissolutionprototype Time (min) Dissolution RSD* Dissolution RSD* 5 28.60% 5% 8.70%12.00% 10 58.40% 10% 20.00% 11.30% 20 79.00% 20% 38.30% 11.40%*Relative standard deviation

TABLE 2 Illustrative dissolution profiles of 1, 3.5, and 10 mg “3minute” zolpidem lozenges using the modified USP dissolution method II.(500 ml of pH 6.8 phosphate buffer at a 37° C. and paddle speed of 15rpm). 1 mg “3 minute” 3.5 mg “3 minute” 10 mg “3 minute” Lozengedissolution prototype dissolution prototype dissolution prototype Time(min) Dissolution RSD Dissolution RSD Dissolution RSD 5 28.70% 11.60%42.40% 11.14% 28.60% 19.90% 10 46.90% 9.30% 70.20% 6.53% 58.40% 10.40%15 60.40% 6.70% 81.00% 7.23% 20 70.50% 5.20% 84.30% 7.14% 79.00% 5.10%

In some embodiments, the compositions of the present invention providecomplete buccal and/or sublingual dissolution in about 2 minutes or lessfollowing administration. The quick-dissolving tablets of the presentinvention usually provide complete buccal and/or sublingual dissolutionin less than about 0.5 minutes, alternatively in less than about 1minute, alternatively in less than about 1.5 minutes, alternatively inless than about 2 minutes, alternatively in less than about 2.5 minutes,alternatively in less than about 3 minutes, alternatively in less thanabout 4 minutes, alternatively in less than about 5 minutes, oralternatively in less than about 6 minutes.

Generally, the compositions described herein comprise a binary or aternary buffer system, the system comprised of at least one protondonating (acidic) component and at least one proton accepting (basic)component. The components of the buffer system are selected such thattheir buffering capacity is greatest (the buffer system has a pK value)at a pH of from about 7.2-11.0, usually at a pH of about, for example,7.2, 7.6, 7.8, 8.0, 8.3, 8.5, 8.8, 9.0, 9.4, 9.5, 9.6, 9.7, or 9.8.

In preferred embodiments, the binary buffer system raises the pH ofsaliva to a pH greater than about 7.2, 7.6, 7.8, 8.0, 8.3, 8.5, or 8.8,irrespective of the starting pH of saliva. In other embodiments, thebinary buffer system raises the pH of saliva to a pH greater than about9.0, 9.4, 9.5, 9.6, 9.7, or 9.8 (e.g., about 9-11), irrespective of thestarting pH of saliva.

Preferably, the buffer system comprises a carbonate and a bicarbonatecomponent. For example, the carbonate salt can be selected from thegroup consisting of sodium carbonate, potassium carbonate, calciumcarbonate, ammonium carbonate, and magnesium carbonate. The bicarbonatesalt can be selected from the group consisting of sodium bicarbonate,potassium bicarbonate, calcium bicarbonate, ammonium bicarbonate, andmagnesium bicarbonate. In a preferred embodiment, the binary buffersystem comprises sodium carbonate and sodium bicarbonate. In anotherpreferred embodiment, the sodium bicarbonate is dessicant-coated sodiumbicarbonate. The cations of the carbonate and the bicarbonate componentscan be the same or different.

The concentration of each buffer system component is tailored such thatthe final salivary pH is achieved and sustained for a period of time,e.g., for at least about 2 minutes, at least about 5 minutes, at leastabout 10 minutes, at least about 20 minutes, or at least about 60minutes. This typically involves a sensory and safety trial and errortype of procedure of adding various amounts of each buffer systemcomponent and then measuring the final pH over time. In this way,selection of an appropriate weight ratio for each buffer systemcomponent can be determined. For example, the weight ratio of carbonatesalt to bicarbonate salt can be from about 1:10 to about 10:1,preferably from about 1:5 to about 5:1, more preferably from about 1:4to about 4:1 or from about 1:3 to about 3:1, and still more preferablyfrom about 1:2 to about 2:1.

In some embodiments, the amount of bicarbonate salt is greater than orequal to the amount of carbonate salt, and the weight ratio of carbonatesalt to bicarbonate salt is from about 1:1 to about 1:10, preferablyfrom about 1:1 to about 1:5, and more preferably from about 1:1 to about1:2, e.g., 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8,1:1.9, or 1:2. Alternatively, the amount of bicarbonate salt is lessthan or equal to the amount of carbonate salt, and the weight ratio ofcarbonate salt to bicarbonate salt is from about 1:1 to about 10:1,preferably from about 1:1 to about 5:1, and more preferably from about1:1 to about 2:1, e.g., 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1,1.7:1, 1.8:1, 1.9:1, or 2:1. In some embodiments, the combined amount ofcarbonate salt and bicarbonate salt is greater than or equal to theamount of zolpidem, and the weight ratio of carbonate salt andbicarbonate salt to zolpidem is preferably from about 1:1 to about 10:1,e.g., 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or 10:1.Alternatively, the combined amount of carbonate salt and bicarbonatesalt is less than or equal to the amount of zolpidem, and the weightratio of carbonate salt and bicarbonate salt to zolpidem is preferablyfrom about 1:1 to about 1:10, e.g., 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7,1:8, 1:9, or 1:10.

In some embodiments, the binary buffer system used in compositionsdescribed above comprises a carbonate salt such as sodium carbonate anda bicarbonate salt such as sodium bicarbonate, wherein the carbonatesalt and the bicarbonate salt are in a carbonate:bicarbonate ratio offrom about 1:1.0 to about 1:1.4 by weight, or alternatively from about1:1.0 to about 1:1.2 by weight.

In other embodiments, the bicarbonate can be used by itself to promoteselective absorption of zolpidem.

Other buffer systems are suitable for use in the compositions of thepresent invention, in addition to or in substitution of a carbonate andbicarbonate buffer system. For example, in an alternative embodiment,the buffer system comprises a carbonate salt or a bicarbonate salt and asecond buffering agent such as a metal oxide, a citrate salt, aphosphate salt, a borate salt, an ascorbate salt, an acetate salt, andalkaline starch. In another alternative embodiment, the buffer systemcomprises a metal oxide and a citrate, phosphate, or borate salt. In yetanother alternative embodiment, the buffer system is a ternary buffersystem comprising a carbonate salt, a bicarbonate salt, and a thirdbuffering agent such as a metal oxide, a citrate salt, a phosphate salt,a borate salt, an ascorbate salt, an acetate salt, and alkaline starch.In still yet another alternative embodiment, the buffer system comprisesa carbonate salt or a bicarbonate salt and two or more buffering agentsselected from the group consisting of a metal oxide, a citrate salt, aphosphate salt, and a borate salt.

In still other embodiments, the pharmaceutical compositions comprise acarrier comprising at least one binder and at least one disintegratingagent in such relative proportion to provide a buccal or sublingualdissolution time of about 5 minutes or less, preferably about 2 minutesor less, following administration. Preferably, the ratio of the binderto the disintegrating agent is from about 0.1 to about 10.0, morepreferably from about 0.1 to about 1.0, and most preferably from about0.26 to about 0.79. However, one skilled in the art will appreciate thatthe compositions of the present invention can be made without anybinders, e.g., to produce a highly friable dosage form.

In a preferred embodiment, the zolpidem is delivered across an oralmucosa selected from the group consisting of the sublingual mucosa, thebuccal mucosa, and a combination thereof. In a particularly preferredembodiment, the composition is administered sublingually so that thezolpidem is delivered across the sublingual mucosa.

In preferred embodiments of the present invention, the zolpidem isformulated in a binary buffer system comprising sodium carbonate andsodium bicarbonate. Such compositions are preferably formulated in theform of a lozenge, candy, or dissolving tablet (e.g., slow-dissolvingtablet or quick-dissolving tablet) for sublingual administration. As aresult, upon sublingual administration, zolpidem is delivered across thesublingual mucosa. In another preferred embodiment, the sodiumbicarbonate is dessicant-coated sodium bicarbonate. A combined weightpercent of sodium carbonate and sodium bicarbonate that is greater thanor equal to the weight percent of zolpidem is also preferred.

In some embodiments, the composition comprises from about 0.4, 0.45, or0.5 to about 1.5, 1.6, 1.7, or 1.8 weight percent zolpidem; from about6.0 to about 10.0 weight percent sodium carbonate; and from about 9.0 toabout 13.0 weight percent dessicant-coated sodium bicarbonate. In apreferred embodiment, the composition comprises about 0.47, 0.8, or 1.7weight percent zolpidem; about 8.0 weight percent sodium carbonate; andabout 11.0 weight percent dessicant-coated sodium bicarbonate. Suchcompositions are preferably in the form of a lozenge or candy with amass of from about 100 to about 300 mg, e.g., about 100, 110, 120, 130,140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270,280, 290, and 300 mg. The lozenges or tablets dissolve in a subject'smouth at a very rapid rate, e.g., within about 2-3 minutes followingadministration.

In certain other instances, the composition comprises from about 0.4,0.45, or 0.5 to about 1.5, 1.6, 1.7, or 1.8 weight percent zolpidem;from about 5.0 to about 9.0 weight percent sodium carbonate; and fromabout 7.0 to about 11.0 weight percent sodium bicarbonate. In apreferred embodiment, the composition comprises about 0.47, 0.8, or 1.7weight percent zolpidem; about 7.0 weight percent sodium carbonate; andabout 9.0 weight percent sodium bicarbonate. Such compositions arepreferably in the form of a dissolving tablet such as a slow-dissolvingtablet or a quick-dissolving tablet of from about 100 to about 300 mg,e.g., about 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210,220, 230, 240, 250, 260, 270, 280, 290, and 300 mg. The quick-dissolvingtablets dissolve in a subject's mouth at a rapid rate, e.g., withinabout 5 minutes following administration, and the slow-dissolvingtablets dissolve in a subject's mouth at a slower rate, e.g., withinabout 10 minutes following administration.

V. Methods

In carrying out the methods of the present invention for treating MOTNinsomnia, the appropriate effective dosage to be administered to asubject can be evaluated in an appropriate patient population that hasbeen selected based on factors such as age, weight, the number of hoursof time in bed remaining, and/or the ability of a subject to metabolizezolpidem. For example, a dose of about 2 mg to about 5 mg can beadministered to a subject who awakens and still has about 4 or 5 hoursof time in bed remaining. Similarly, a dose of about 3 mg to about 5 mgcan be administered to non-elderly subjects (i.e., subjects younger than65 years of age) with a normal capacity to metabolize zolpidem. If thesubject awakens with about 2-4 hours of time in bed remaining, a dose ofabout 0.5 mg to about 2.5 mg can be administered. Likewise, subjectswith a diminished capacity to metabolize zolpidem (i.e., subjects 65years of age and older) can be administered a portion of a dose thatwould be administered to a subject with a normal capacity to metabolizezolpidem, for example, a half-tablet dose. One of skill in the art willappreciate that there can be some variability in the dose provided tosome individuals. For example, hepatically-impaired individuals may usea very low dose such as that typically provided for an elderly patient.

Typically, an effective amount of zolpidem is administered to a subjectwith MOTN insomnia on an as needed basis, i.e., pro re nata. That is,the individual had previously fallen asleep, and the sleep time has beeninterrupted with at least about 2, 3, 4, or 5 hours of time in bedremaining. Generally, in practicing the present methods, zolpidem is notadministered prophylactically, or before initial onset of sleep.

Typically, the methods are carried out by administering a composition ofthe present invention as described above. Compositions of particularinterest for treating MOTN insomnia contain less than about 5 mg ofzolpidem or a salt thereof. In certain embodiments, the zolpidem can beadministered in a quick-dissolving tablet or lozenge. Efficient deliveryof zolpidem can be achieved using a formulation with a binary or aternary buffer system, for example with carbonate and bicarbonatecomponents, as described above.

Administration of the compositions of the present invention ispreferably carried out via any of the accepted modes of administrationto the mucous membranes of the oral cavity. Examples of suitable sitesof administration within the oral mucosa include, without limitation,the mucous membranes of the floor of the mouth (sublingual mucosa), thecheeks (buccal mucosa), the gums (gingival mucosa), the roof of themouth (palatal mucosa), the lining of the lips, and combinationsthereof. These regions differ from each other with respect to theiranatomy, drug permeability, and physiological response to drugs.Preferably, the compositions of the present invention are administeredto the sublingual mucosa, buccal mucosa, or a combination thereof.

The oral mucosa, possessing a rich blood supply and suitable drugpermeability, is an especially attractive route of administration forsystemic drug delivery. Furthermore, delivery of a therapeutic agentacross the oral mucosa bypasses hepatic first pass metabolism, avoidsenzymatic degradation within the gastrointestinal tract, and provides amore suitable enzymatic flora for drug absorption. As used herein, theterm “sublingual delivery” refers to the administration of a therapeuticagent across the mucous membranes lining the floor of the mouth and/orthe ventral tongue. The term “buccal delivery” as used herein refers tothe administration of a therapeutic agent across the mucous membraneslining the cheeks.

VI. Examples

The following examples are offered to illustrate, but not to limit, theclaimed invention.

Example 1 Low Dose Zolpidem Lozenge Compositions

Individuals suffering from middle-of-the-night insomnia are givenlozenges containing 0 mg, 1.0 mg, 1.75 mg, or 3.5 mg zolpidem forsublingual delivery that are prepared according to the formulations setforth in Table 3. TABLE 3 Low dose zolpidem lozenge formulations.Quantity (mg/lozenge) Strength Component Placebo 1.0 mg 1.75 mg 1.75 mg3.5 mg Zolpidem hemitartrate 0 1.0 1.75 1.75 3.5 Pharmaburst ™ B2 143142 70 141.25 139.5 Consisting of: mannitol sorbitol crospovidonesilicon dioxide Croscarmellose sodium 10 10 5 10 10 Sodium carbonate 1717 8.5 17 17 Sodium bicarbonate 23 23 11.5 23 23 Natural and artificial6.5 6.5 3.25 6.5 6.5 spearmint FONA# 913.004 Silicon dioxide 5.5 5.52.75 5.5 5.5 Sucralose 1.5 1.5 0.75 1.5 1.5 Magnesium stearate 3.5 3.51.75 3.5 3.5 Total lozenge weight 210 210 105 210 210

The individuals self-administer one lozenge of the above formulationswhen their sleep is interrupted and they have at least 2 hours of sleeptime remaining. Upon awakening, the individuals provide a subjectiveself-assessment of any residual sedative effects and are given thefollowing psychomotor and memory tests to evaluate any residual sedativeeffects: a digit symbol substitution test (DSST), a choice reaction time(CRT), a symbol copy test (SCT), and a Buschke Memory Recall Test.

Individuals receiving a placebo lozenge are generally unable to fallback asleep and therefore do not feel refreshed in the morning.Individuals receiving lozenges containing 1.0 mg, 1.75 mg, or 3.5 mgzolpidem fall asleep within about 20 minutes after self-administrationof the lozenge and exhibit no or minimal residual sedative effects asevaluated by subjective self-assessment and any of the above-referencedpsychomotor and memory tests.

Example 2 Pharmacokinetic and Pharmacodynamic Investigation of Low DoseZolpidem Lozenge Compositions

This example provides an evaluation of the daytime dose-dependentpharmacokinetic and pharmacodynamic effects of the 1.0 mg, 1.75 mg, and3.5 mg zolpidem lozenges described in Table 3 above.

SUMMARY

Currently, no medications are available to be used on a pro re natabasis for patients who have middle-of-the-night (MOTN) awakening and whohave difficulty falling back asleep. An appropriate therapeutic agentfor such insomnia would enable patients to return to sleep rapidly andwake up in the morning without residual effects. This study illustrates,inter alia, that the low dose zolpidem lozenges of the present inventionenhance rapid systemic delivery of zolpidem without affecting otherpharmacokinetic parameters.

Healthy adults (n=24; mean age=37.6 yrs) participated in thisdouble-blind, placebo-controlled, 4-way crossover study of 2 consecutivedays of morning dosing with placebo, or 1 mg, 1.75 mg, or 3.5 mg of thelow dose zolpidem lozenges of the present invention. After morningdosing, on Day 1 of each period, pharmacodynamic endpoints (DSST, PVT,VAS-sedation, SCT, and Buschke) were evaluated at pre-dose and at 20minutes 1, 1.5, 2, 3, 4, and 5 hours post-dose. On Day 2, repeated bloodsamples for pharmacokinetic assessment were drawn over 12 hours.

Baseline DSST scores (±SE) were 57.6±2.9, 58.0±3.1, 58.4±2.3, and56.9±2.7 for the placebo, 1 mg, 1.75 mg, and 3.5 mg zolpidem lozenge,respectively. Significant reductions in DSST. scores were found for the1.75 mg and 3.5 mg zolpidem lozenges at the beginning of 20 minutes(−6.6; p=0.0132 and −14.8; p<0.001, respectively) and lasted for 1.5hours post-dose. Other endpoints showed results similar to DSST. MeanT_(max) was 36.0, 37.9, and 37.9 minutes for the 1 mg, 1.75 mg, and 3.5mg zolpidem lozenge, respectively. Zolpidem C_(max) and AUC weredose-proportional. The 1.75 mg and 3.5 mg zolpidem lozenges reachedsedation plasma levels (about 20 ng/ml) within 15 minutes, and theselevels were maintained for 15 to 240 minutes.

Low dose zolpidem lozenges provide daytime sedative properties at a doseand a T_(max) of less than half of the approved dose of peroral (PO)zolpidem (10 mg) in adults. This study demonstrates that the low dosesublingual zolpidem lozenges of the present invention can be used toshorten sleep onset upon MOTN administration.

Methods

Design

This was a four-way crossover, placebo controlled, randomized doubleblind study with healthy male (n=13) and female (n=11) volunteers. Eachtreatment period consisted of two single-dose consecutive treatmentdays, and each treatment was separated by a wash-out period of 6 days ormore. During each period, lozenges were administered approximately 24hours apart, and the subjects received the same treatment on each day.During each period, in order to avoid any learning or drug-anticipatoryresponse, the pharmacodynamic effects were measured on Day 1 and bloodsamples drawn on Day 2 for pharmacokinetic assessment.

Pharmacodynamic assessment consisted of measurements of sedation,memory, and vigilance tests. The sedative effects were quantified by adecrease in post- to pre-dose scores on a Digit Symbol Substitution Test(DSST) and self-rated assessment sedation on a Visual Analog Scale(VAS). Vigilance was assessed by an increase in post- to pre-dose scoresby measurement of reaction time and number of lapses in reaction todigital stimuli using a computerized Psychomotor Vigilance Test (PVT). Adecrease in post- to pre-dose scores on a Buschke Word Recall Test(Buschke) was used for memory effects. Additionally, a Symbol Copy Test(SCT) was used for measurement of simple cognitive function. The resultswere statistically analyzed using SAS, ANOVA procedures and significancewas assessed using Dunnett's test for comparison.

Serial blood samples were drawn for up to 12 hours at pre-dose, 5, 10,20, 30, and 45 minutes and 1, 2, 2.5, 3, 3.5, 4, 5, 6, 8, and 12 hours.Non-compartmental pharmacokinetic parameters were estimated using theWinNonlin program (Pharsight Corp.; Palo Alto, Calif.). The parametersestimated were AUC and partial AUC, C_(max), t_(max), and t_(1/2).

Additionally, the plasma levels of the 1.0 mg, 1.75 mg, and 3.5 mgzolpidem lozenges were predicted following single compartment firstorder input and output modeling of data for a 10 mg zolpidem lozengeusing the following equation:Ct=D*K01/V/(K01−K10)*EXP(−K10*T)−EXP(−K01*T),wherein Ct=predicted plasma concentration, D=dose, V=apparent volume ofdistribution, T=time, K01=absorption rate constant, and K10=theelimination rate constant. The values for V, K01 and K10 were obtainedby fitting the plasma data from the 10 mg zolpidem lozenge (i.e., 3minute dissolution lozenge swallowed every 2 minutes) to the aboveequation. Unless otherwise indicated, standard deviation is the varianceparameter associated with the mean values.ResultsPharmacokinetics

Zolpidem was rapidly absorbed and eliminated from each of the three lowdose sublingual lozenge formulations. The plasma profiles of the threelozenge formulations are shown in FIG. 1, and summary statistics of thepharmacokinetic parameters are described in Table 4. Overall, thet_(max) and C_(max) of the three lozenge formulations were significantlyshorter and higher, respectively, than the values either predicted bymodeling of the 10 mg data (see, FIG. 2) or reported in the literature.TABLE 4 Mean (% CV) bioavailability parameters of the low dose zolpidemlozenges. Mean Bioavailability AUC Rate Dose C_(max) t_(max) AUC 0-12 hr0-20 mn (ng/ml per mg ng/ml min ng · hr/ml ng · hr/ml min) 1.0 17.7736    65.31 1.53 0.49 (33%) (30%) (40%) (42%) 1.75 32.17 37.9 119.543.20 0.85 (32%) (42%) (40%) (42%) 3.5 64.14 37.9 229.42 5.80 1.69 (33%)(40%) (40%) (41%)

In particular, this pharmacokinetic study provided the following keyobservations:

-   1. The 3.5 mg lozenge produced a C_(max) of about 64 ng/ml in about    38 minutes with an AUCO-12 hr of about 229 ng.hr/ml. The mean value    AUCO-20 min was 5.80 ng.hr/ml.-   2. The values of the C_(max) and t_(max) for the 1.75 mg lozenge    were about 32 ng/ml and 38 minutes, respectively. The values of    AUCO-12 hr and AUCO-20 min were 119.54 and 3.20 ng.hr/ml,    respectively.-   3. The values of the C_(max) and t_(max) for the 1 mg lozenge were    about 18 ng/ml and 36 minutes, respectively. The values of AUCO-12    hr and AUCO-20 min were 65.31 and 1.53 ng.hr/ml, respectively.-   4. The observed values of C_(max) of all three lozenge formulations    were significantly higher than the values predicted by    pharmacokinetic modeling of the 10 mg data.-   5. The pharmacokinetics of the three lozenge formulations were    proportional to the dose.    Pharmacodynamics

Digit Symbol Substitution Test (DSST): The DSST is an objective measureof sedation. As shown in FIG. 3, the 1.75 mg and 3.5 mg zolpidemlozenges produced peak changes in DSST scores within 20 to 60 minutes ofadministration, and scores returned to baseline within 3 to 4 hours ofadministration. These scores were significantly different from baselinefor up to about 90 minutes. The DSST scores for the 1 mg zolpidemlozenge were statistically similar to that of the placebo.

FIG. 4 shows that the relationship between plasma levels of the zolpidemlozenges and the DSST response is characterized by an anti-clockwisehysteresis loop, which is typical for sedative-hypnotics. This indicatesthat the rapid pharmacodynamic effects are primarily due to the rapidbioavailability of the zolpidem present in the lozenges and not due toany changes in the receptor pharmacology of the drug.

One of the most surprising findings from the DSST scores for the 3.5 mgzolpidem lozenge is that the sedative response is more rapid than thevalues reported in the literature for 5 mg and 10 mg peroral (PO)Ambien® (see, Greenblatt et al., Clin. Pharmacol. Therap., 64:553-561(1998); Greenblatt et al., Clin. Pharmacol. Therap., 64:661-671 (1998)).In particular, FIG. 5 shows that the 3.5 mg zolpidem lozenge was capableof inducing sleep more rapidly than both 5 mg and 10 mg PO Ambien®, butdid not cause the excessive sedation associated with 10 mg PO Ambien®.

Self-rated assessment of sedation on VAS: Unlike DSST, the subjectivesedative effects of the 1.75 mg and 3.5 mg zolpidem lozenges weresimilar (FIG. 6). The Visual Analog Scale (VAS) scores for these lowzolpidem doses were statistically different than placebo for up to 2hours.

Vigilance changes as measured by PVT: The 3.5 mg zolpidem lozenge alsoimpaired vigilance, as measured by reaction times using a PsychomotorVigilance Test (PVT). FIG. 7 shows that the reaction time scores for the3.5 mg zolpidem lozenge were statistically different for up to about 90minutes.

Memory impairment (Buschke): Except for the significant effect seen at20 minutes with the 3.5 mg zolpidem lozenge, the drug effects werecomparable to that of the placebo.

Simple motor task impairment (SCT): The effects of the three lozengeformulations were comparable to that of the placebo.

CONCLUSIONS

-   1. Surprisingly, the zolpidem blood levels established at several    time points up to 30 mintues after dosing with the 3.5 mg zolpidem    lozenge exceeded those reported in the literature for PO Ambien®    doses up to and including 10 mg. In fact, the 3.5 mg zolpidem    lozenge was superior to 10 mg PO Ambien® (which contains nearly 3    times the dose of zolpidem) because it provided a significantly    greater sedative effect at 30 minutes as measured by DSST testing.-   2. The C_(max) (maximum plasma concentration) of zolpidem from the    low dose zolpidem lozenges was about 30% higher than the values    predicted by pharmacokinetic modeling of data for a 10 mg zolpidem    lozenge. The mean C_(max) (64 ng/ml) of the 3.5 mg zolpidem lozenge    was in the same range as the values reported for 5 mg PO Ambien®.    Further, both 1.75 mg and 3.5 mg zolpidem lozenges produced plasma    levels at 30 minutes or earlier that have been reported in the    literature to produce sedative effects.-   3. The low dose zolpidem lozenges achieved maximum plasma    concentrations in about 36 to 38 minutes. A t_(max) of about 35    minutes was significantly earlier than the t_(max) of 1 to 1.5 hours    typically reported for 5 mg and 10 mg PO zolpidem (Ambien®),    eszopiclone (Lunesta™), zaleplon (Sonata®), and remelteon    (Rozerem™).-   4. The pharmacodynamic data described above demonstrate that the    1.75 mg and 3.5 mg zolpidem lozenges produced rapid    sedative-hypnotic effects without the risk of anterograde amnesia or    falling in night, which are side-effects typical of higher PO    Ambien® doses.-   5. The pharmacokinetic and pharmacodynamic response to the low dose    zolpidem lozenges was proportional to the dose. Therefore, the    pharmacology of zolpidem at a dose range of between about 1 mg to    3.5 mg, unlike that of 5 mg PO Ambien®, is expected to produce a    consistent and predictable response.

6. The pharmacodynamic data described above clearly demonstrate thesedative effects of 1.75 mg and 3.5 mg zolpidem lozenge formulations,which included rapid onset of action. In fact, the onset of action andpeak effects as defined by both DSST (objective) and VAS (subjective)occurred within 20 minutes. In contrast, 5 mg PO Ambien® produced peakDSST effects in about 60 minutes and the magnitude of the response wasonly about 50% of that seen with the 3.5 mg zolpidem lozenge. The levelsof decline in DSST (surrogate for sedation) scores were comparable tothose seen with marketed hypnotics.

-   7. During the pharmacodynamic portion of the study, low dose    zolpidem lozenges containing 1.75 or 3.5 mg zolpidem produced peak    sedative effects (as measured by DSST and VAS) within about 20    minutes of dosing.-   8. The 3.5 mg zolpidem lozenge also impaired vigilance (as measured    by reaction times on PVT). The 1.75 mg zolpidem lozenge had no    effect on subjects who were non-elderly adults.-   9. None of the doses of zolpidem present in the low dose zolpidem    lozenges impaired performance on a memory test (Buschke) or a simple    motor task capability test (SCT).

Example 3 Low Dose Zolpidem Tablet Composition

An immediate release peroral (PO) tablet containing a low dose ofzolpidem can be prepared according to the formulation set forth in Table5. TABLE 5 Low dose zolpidem tablet formulation. Component Quantity (mg)Zolpidem Hemitartrate 3.5 Povidone K29/32 15.0 Sodium Starch Glycolate(SSG) 7.5 Starch 1500 15.0 Lactose Fast Flow 82.0 Prosolv SMCC 90 65.5Sodium bicarbonate 40 Magnesium Stearate 1.5 Total 230Manufacturing Process

Dispensing: Screen the zolpidem hemitartrate and excipients throughscreen #30. Dispense the required quantities of each ingredient.

Blending:

-   1. Transfer the zolpidem hemitartrate and Povidone K 29/32 to a    V-Shell blender and blend for 2 min.-   2. Add SSG and Starch 1500 to Step 1 and blend for another 2 min.-   3. Add Lactose Fast Flow and Prosolv SMCC 90 to Step 2 and blend for    another 10 min.-   4. Mix an equal amount of the blend from Step 3 with magnesium    stearate or sodium stearyl fumarate and transfer the mixture back to    the V-Shell blender via screen # 30. Blend for 3 min.

Compression: Compress the final blend from Step 4 on a rotary press to atarget tablet weight of 210 mg.

All publications and patent applications cited in this specification areherein incorporated by reference as if each individual publication orpatent application were specifically and individually indicated to beincorporated by reference. Although the foregoing invention has beendescribed in some detail by way of illustration and example for purposesof clarity of understanding, it will be readily apparent to those ofordinary skill in the art in light of the teachings of this inventionthat certain changes and modifications may be made thereto withoutdeparting from the spirit or scope of the appended claims.

1. A pharmaceutical composition suitable for absorption by the oralmucosa in the treatment of MOTN insomnia, said composition comprisingfrom about 0.5 mg to about 4.0 mg of zolpidem or a salt thereof and apharmaceutically acceptable excipient.
 2. A pharmaceutical compositionof claim 1, wherein said pharmaceutical composition comprises from about0.5 to about 4.0 mg of zolpidem hemitartrate.
 3. A pharmaceuticalcomposition of claim 1, wherein said pharmaceutical compositioncomprises about 1.0 mg zolpidem.
 4. A pharmaceutical composition ofclaim 1, wherein said pharmaceutical composition comprises about 1.75 mgzolpidem.
 5. A pharmaceutical composition of claim 1, wherein saidpharmaceutical composition comprises about 3.5 mg zolpidem.
 6. Apharmaceutical composition of claim 1, wherein said pharmaceuticalcomposition comprises a binary buffer system.
 7. A pharmaceuticalcomposition of claim 6, wherein said buffer system raises the pH ofsaliva to a pH greater than about 8.5, irrespective of the starting pHof saliva.
 8. A pharmaceutical composition of claim 6, in the form of aquick-dissolving tablet or lozenge.
 9. A pharmaceutical composition ofclaim 8, which provides complete buccal and/or sublingual dissolution inabout 5 minutes or less following administration.
 10. A pharmaceuticalcomposition of claim 6, wherein said buffer system comprises a carbonateand a bicarbonate.
 11. A pharmaceutical composition of claim 10, whereinsaid carbonate and bicarbonate are present in a carbonate:bicarbonateratio of about 1:1.0 to about 1:1.2 by weight.
 12. A pharmaceuticalcomposition of claim 10, wherein said buffer system comprises sodiumcarbonate and sodium bicarbonate.
 13. A method of treating insomnia,said method comprising administering to a subject who awakens from sleepand desires return to sleep within 30 minutes and sleep for less than 5hours, a single unit dosage composition comprising an effective amountof zolpidem or a salt thereof, formulated for delivery of zolpidemacross the subject's oral mucosa, wherein said effective amount is anamount of less than 1.30×10⁻⁵ moles of zolpidem, and is an amountsufficient to produce a plasma concentration between about 25 ng/ml andabout 50 ng/ml within 20 minutes of administration, when evaluated in anappropriate patient population.
 14. A method in accordance with claim13, wherein said composition is administered pro re nata.
 15. A methodin accordance with claim 13, wherein said composition is aquick-dissolving tablet or lozenge formulated for buccal and/orsublingual delivery of zolpidem.
 16. A method in accordance with claim13, wherein said composition comprises a binary buffer system thatraises the pH of said subject's saliva to a pH greater than about 8.5,irrespective of the starting pH of saliva.
 17. A method in accordancewith claim 13, wherein said composition comprises from 0.5 to 4.75 mg ofzolpidem hemitartrate and a binary buffer system of sodium carbonate andsodium bicarbonate that raises the pH of said subject's saliva to a pHgreater than about 8.5, irrespective of the starting pH of saliva.
 18. Amethod of treating MOTN insomnia in a subject, comprising: administeringto said subject a pharmaceutical composition comprising zolpidem or asalt thereof in an amount of less than 1.30×10⁻⁵ moles of zolpidem,wherein said administering is on an as-needed basis, and whereindelivery of zolpidem occurs across the subject's oral mucosa to producea blood level of zolpidem in said subject between about 25 ng/ml andabout 50 ng/ml within about 20 minutes of administration and less than20 ng/ml at a time 4 hours after administration.
 19. A method inaccordance with claim 18, wherein said composition comprises at leastone pH-adjusting agent.
 20. A method in accordance with claim 18,wherein said composition comprises a binary buffer system that raisesthe pH of said subject's saliva to a pH greater than about 8.5,irrespective of the starting pH of saliva.
 21. A method in accordancewith claim 18, wherein said composition comprises zolpidem hemitartrate.22. A method in accordance with claim 21, wherein said compositioncomprises from 0.5 to 4.75 mg of zolpidem hemitartrate.
 23. A method inaccordance with claim 21, wherein said composition comprises from 1.5 to2.5 mg of zolpidem hemitartrate.
 24. A method in accordance with claim21, wherein said composition comprises from 3.0 to 3.75 mg of zolpidemhemitartrate.
 25. A method in accordance with claim 18, wherein saidcomposition provides 50% of the maximum plasma concentration (C_(max))in 10 minutes or less following administration.
 26. A method inaccordance with claim 25, wherein said composition comprises less than a5 mg dose of zolpidem hemitartrate and a binary buffer system consistingof a carbonate salt and a bicarbonate salt.
 27. A method in accordancewith claim 18, wherein said composition is in the form of aquick-dissolving sublingual tablet or lozenge.
 28. A method inaccordance with claim 18, wherein delivery of zolpidem occurs across atleast one of the sublingual or buccal mucosa.
 29. A method of treatinginsomnia in a subject, comprising: administering to said subject apharmaceutical composition comprising zolpidem or a salt thereof,wherein said composition provides delivery of zolpidem across thesubject's oral mucosa, wherein said subject is a subject who awakensfrom sleep and desires to resume sleep for less than 5 hours, andwherein said composition produces sleep within 30 minutes of dosing andthe dose is such that it does not produce residual sedative effects whensaid subject is awakened at a time 4 hours after dosing.
 30. A method inaccordance with claim 29, wherein said sleep is polysomnography stage 1sleep at the onset of sleep.
 31. A method in accordance with claim 29,wherein said composition produces a blood level of zolpidem in saidsubject between about 25 ng/ml and about 50 ng/ml within 20 minutes ofadministration.
 32. A method in accordance with claim 29, wherein saidcomposition produces a blood level of zolpidem in said subject less than20 ng/ml at a time 4 hours after administration.
 33. A method inaccordance with claim 32, wherein said composition provides 50% of themaximum plasma concentration (C_(max)) in 10 minutes or less followingadministration.
 34. A method in accordance with claim 29, wherein saidcomposition comprises zolpidem hemitartrate.
 35. A method in accordancewith claim 29, wherein said composition comprises at least onepH-adjusting agent.
 36. A method in accordance with claim 29, whereinsaid composition comprises a binary buffer system that raises the pH ofsaid subject's saliva to a pH greater than about 8.5, irrespective ofthe starting pH of saliva.
 37. A method in accordance with any of claims29 to 36, wherein said composition is a solid unit dosage form.
 38. Amethod in accordance with claim 36, wherein said composition is in theform of a quick-dissolving sublingual tablet or lozenge.
 39. A method inaccordance with claim 36, wherein said composition comprises from 1.5 to2.5 mg of zolpidem hemitartrate.
 40. A method in accordance with claim36, wherein said composition comprises from 3.0 to 3.75 mg of zolpidemhemitartrate.
 41. A method in accordance with claim 36, wherein saidcomposition comprises from 1.5 to 2.5 mg of zolpidem hemitartrate andsaid binary buffer system consists of sodium carbonate and sodiumbicarbonate.
 42. A method in accordance with claim 36, wherein saidcomposition comprises from 3.0 to 3.75 mg of zolpidem hemitartrate andsaid binary buffer system consists of sodium carbonate and sodiumbicarbonate.
 43. A method in accordance with claim 29, wherein thezolpidem is delivered across at least one of the sublingual or buccalmucosa.